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6 l(ji/nr\ 7<3 ' / 




HARVARD 
COLLEGE 
LIBRARY 



THB 



COLLECTED WORKS 



SIR HUMPHRY DAVY, Babt. 



THE 



2.?f 

/r 



COLLECTED WORKS 



OP 



'yy 



SIR HUMPHRY j?AVY, Bart. 

LL.D. F.R.S. 

FOBBIGN A8S00U.TB OF THS INSTITUTB OF FIU5CE, ETC. 

EDITED BT HIS BBOTHEB, 

JOHN DAVY, M.D. F.R.S. 



\^ 



VOL. vn. , 

DISCOURSES DELIVERED BEFORE THE ROYAL SOCIETY; 

AND 

AGRICULTURAL LECTURES, PART I. 



LONDON: 
SMITH, ELDER AND CO. CORNHILL. 

1840. 



Lossos: 
pmnmD bt nvwAST avo mvbbat, ou> bailst. 



DISCOURSES 



DBLIYBBBD BBPOBB 



THE ROYAL SOCIETY 



ELEMENTS 



AGRICULTURAL CHEMISTRY, 

PART L 



LONDON: 

SMITH, ELDER AND CO, CORNHILL. 

1840. 



Chcml^.l 



[Oirivo to circumstances connected with the interests of copy-Ti|fht, it 
has been necessary to give the author's Lectures on Agricultural 
Chemistry, in two volumes, conjoined with other topics ; thus, in the 
present volume they are preceded by his Discourses delivered before 
the Royal Society in the capacity of President at the anniversary meetings ; 
by some delineations of character of distinguished men, extracted from 
his unpublished Lectures on Chemistry ; and by aportionof a Journal of 
a tour in Ireland in 1 806 ; and in the next volume they will be followed by 
examples of the same Lectures ; showing, however imperfectly, his manner 
of addressing a mixed audience, such as that which always assembled in 
the theatre of the Royal Institution, and the kind of eloquence, acknow- 
ledged by all who ever heard him, by wldch he succeeded in fixing the 
attention and exciting an interest in matters of science. 

His Discourses delivered before the Royal Society were published at 
the request of the Council of the Society, and, as has been mentioned in 
the first volume, shortly after his last election to the office of President, 
and when labouring under serious illness, the first attack of that malady 
which ultimately proved fatal. Amongst papers which have come into 
the editors possession since that volume was written, there is one expres- 
sive of the feeling of the Society towards him as President, and specially 
referring to these Discourses, which it may be right to insert here. It is, 
verbatim, as follows, written on parchment :— 

<< At a meeting of the Royal Society, held on Thursday, the 16th of 
November, 1827, the President stated from tiie chair, that he was directed 



VIU 

by the Conncil to submit the following resolution to the Society which was 
unaninwusly agreed to : 

" That the regret of the Fellows of the Royal Society be expressed in 
the strongest terms to their late excellent President Sir Humphry 
Davy, Baronet, for the state of health which has unhappHy compelled 
him to relinquish the chair ; together with their thanks for the unremit- 
ting diligence with which he has at all times endeavoured to promote the 
interests of science, and the welfare of the Royal Society, and for the 
learned and eloquent discourses which at each anniyersary during his 
Presidency he concluded the business of the year."] 



:% 

•s.? 









CONTENTS. 



ERRATA. 
Page 6, line 9, /or Patrona rearf Patron. 

275, — 16»/or clastic gum rearf gum-elastic. 
293, — 7, afitr saccharine add matter. 

341, — 31, /or salt rtad salts. _^ 

342, — 15,/or applied read supplied. ^jflW 

\ 
Address of the President on taking the Chair of the Royal Society, I 

for the first tune, December 7th, 1820.— On the Present State \ 

of that Body, and on the Progress and Prospects of Science . 5 

II. 

Disoourse of the President, November 30th, 1821, in announcing 
the Award of two Medals on Sir Godfrey Copley's Donation. 
One to J. P. W. Herschel, Esq., P.R.S., for his yarious Pa- 
pers on Mathematical and Physico-Mathematical Subjects, 
published in the Philosophical Transactions. And the other to 
Captain Edward Sabine, R.A., for his Papers containing an 
Account of his yarious Experiments and Observations, made I 

during the Voyage and Expedition in the Arctic Regions .16 



X CONTENTS. 

Pftfe 
III. 

Discourse of the President, Anniversary, November 90th, 1822, 
on the Characters of some Deceased Fellows : — Sir Henry C. 
Bnglefleld, Bart., Sir JV^llliam Herschel, Dr. Marcet, the Rev. 
Samuel Vince, Dr. Parry, Dr. Cannichael Smith, MM. Hauy, 
Delambre, and BerthoUet. — And on the Award of the Medal 
on Sir Godfrey Copley's Donation, to the Rev. Professor Buck- 
land, for his Paper on the Bones of Hysenas, and other Animals 
found in a Cave at Kirkdale, in Yorkshire.— With General 
Views on the Progress and Prospects of Geology . 28 

IV. 

Discourse of the President, Anniversary, December 1st, 1823, on 
the Characters of Dr. Button, Dr. Jenner, Dr. Baillie, Colonel 
Lambton, Archdeacon Wollaston, Dr. Cartwright, and Mr. Jor- 
dan ; and on the Award of the Copley Medal to John Pond, 
Esq., Astronomer Royal, for his various Papers on Subjects of 
Astronomy, published in the Philosophical Transactions. — With 
Greneral Views of the Present State of Astronomy, and on the 
Accessions made to this Branch of Science, in the Royal Ob- 
servatory at Greenwich . .45 

V. 

Discourse of the President, Anniversary, 1 824. Character of Baron 
Maseres. — Award of the Copley Medal to the Rev. Dr. Brink- 
ley, now Bishop of Cloyne, for his Mathematical and Astronomi- 
cal Papers, published in the Philosophical Transactions. — ^With 
Views on some Refined Questions of Astronomy, and on the 
General Importance and Sublime Views of this Science . 61 

VJ. 

Discourse of the President, Anniversary, November SOth, 1826. 
Character of Mr. William Higgins. — Award of two Copley 
Medals : one to M. Arago, F.R.S., M.R.A.S.P., for his Dis- 
covery of the Property possessed by Bodies in general to be 
affected by Magnetism : and the other to Mr. Peter Barlow, 



CONTfijrTO. jd 

F.R.S.^ ProfeBSor at the Royal Military Academy at Woolwich, 
for his Diflcorery of a Method of Correcting the Errors of the 
CompaflB, arising from the Attraction of the Iton in a Ship . 75 

VII. 

DiflconiBeof the President, Anniyersary, 18S6. — ChaFacters of Tay* 
lor Combe, Esq., and Sir Thomas Stamford Raffles. — Award of 
the Royid Medals to Mr. John Dalton, F.R.S., for his Develop- 
ment of the Theory of Definite Proportions, nsaally called the 
Atomic Theory of Chemistry ; and to James lYory, Esq., F.R.8. 
for his yarions Mathematical Papers, published in the Philo- 
sophical Transactions. And on the Award of the Copley Me* 
dal to James Soath, Esq., F.R.S., for his Observations on Dou- 
ble Stars.— With Genenl Views on the Scientific History and 
Particular Merits of the Subjects for which the Prizes were 
given . . .90 



Adyertisbment . • .113 

Sketch of the Character of Dr. Priestley .115 

Character of Scheele . . . .118 

Character of Pliny the Elder . .120 

Character of Lord Bacon .121 

Character of the Eld^ Bacon . .122 

Character of Newton . . .124 

Character of Mr. Cavendish . .127 

Remarks relative to the Discovery of the Composition of Water . 129 

Speech in Eulogy of Mr. Watt . .141 



Joumalof a Tour in Ireland • . ,146 



XU CONTENTS. 



BLBMXNTS OF AOEICULTURAL CHEMISTRT, IN A C0TJB8B OF 
LECTURES FOB THE BOABD OF AOBICULTURE; DB- 
LIYERBD BETWEEN 1802 AND 1812 . 109 

ADTBRTISBMBNT • .171 

Dedication ...... 173 

Adtertisement to the fourth edition . 175 

Lecture I. 

Introduction. — General Views of the Objects of the Course, and of 
the order in which they are to be discussed • 177 

Lecture II. 

Of the General Powers of Matter which influence Vegetation ; of 
Grayitation, of Cohesion, of Chemical Attraction, of Heat, of 
Light, of Electricity ; Ponderable Substances, Elements of 
Matter, particularly those found in Vegetables ; Laws of their 
Combinations and Arrangements . . 200 

t 

Lecture III. 

On the Organization of Plants. — Of the Boots, Trunks, and Branches. 
— Of their Structure. — Of the Epidermis.— Of the Cortical and 
Albumous Parts. — Of Leaves, Flowers, and Seeds. — Of the 
Chemical Constitution of the Organs of Plants, and the Sub- 
stances found in them. — Of Mucilaginous, Saccharine, Extrac- 
tive, Resinous and Oily Substances, and other Vegetable Com- 
pounds; their Arrangements in the Organs of Plants, their 
Composition, Changes and Uses . . . 232 

Lecture IV. 

On Soils : their Constituent Parts. — On the Analysis of Soils. — 
Of the Uses of the Soil.— Of the Rocks and Strata found he^ 
neath the Soils. — Of the Improvement of Soil . . 901 



CONTENTS. Xiil 

Lbctubb y. 

On the Nature and CkmBtitntion of the Atmosphere, and its In- 
flaence on Vegetables. — Of the Germination of Seeds.— Of the 
Fonctions of Plants in their different Stages of Growth ; with a 
General View of the Progress of Vegetation . 944 



(Continued in Vol. VIII.) 



DIRECTIONS FOR THE PLATES. 



Plate I. . . . 


to face page 202 


II. 


. 226 


III. to V. 


. 226 


VI. 


. 228 


VII. 


. 282 


VIII. . 


. 811 


IX. . . . . 


. 837 


X. 


. 360 



SIX DISCOURSES 

DBLZTSRBD BBFORB 

THE ROYAL SOCIETY 

AT THBIR 

ANNIVEBSARY MEETINGS, 

ON THB 

AWARD OF THE ROYAL AND COPLEY MEDALS; 

PRB€BDBD BT 

AN ADDRESS TO THE SOCIETY, 

Oir TRB 

PROGRESS AND PROSPECTS OF SCIENCE. 



VOL. vu. 



ADVERTISEMENT. 



I HAVE published these Discourses in compliance with 
the wishes of the Council of the Royal Society. I hope 
they will be read by the public in the same spirit in 
which they were heard by the Fellows. They were in- 
tended to communicate general views on the particular 
subjects of science to which they relate, and not minute 
information. They must not be considered as finished 
dissertations; — their principal object was to endeavour 
to keep alive the spirit of philosophical inquiry and the 
love of scientific glory. 

Park'ttreetf Jan. 3, 1887. 



ADDRESS OF THB PRESIDBNT ON TAKING THE CHAIR OF 
THE ROYAL SOCIETY, FOB THE FIRST TIME; DECEMBER 
7th, 18S0.— on the present STATE OF THAT BODY, AND 
ON THE PROGRESS AND PROSPECTS OF SCIENCE. 

Gentlemen, 
I HAVE, on a fonner occasion,* returned you my thanks 
for the distmguished honour you have done me in elect- 
ing me your President I have stated to you my entire 
devotion to your interests, and to the cause of science. 
I do not mean to indulge in any fiirther expression of 
my feelings on this occasion, except to say that they 
are deep, and will be permanent 

But I think it my duty, before I enter upon the de- 
tails of common business, to devote a few words to the 
present state of the Royal Society, its relations to other 
scientific bodies, and the prospects and hopes of science. 

In the early periods of our establishment, when ap- 
paratus was procured with di£Sculty, when the greatest 
philosophers were obliged to labour with their own 
hands to firame their instruments, it was found expe- 
dient to keep in the rooms of the Society a collection of 
all such machines as were likely to be useful in the pro- 
gress of experimental knowledge: and curators and 
operators were employed, by whom many capital expe- 
riments were made under the eyes of the Society. But 
since the improvement of the mechanical and chemical 
arts have afforded great facilities as to the means of 
* At the annlrersary dinner, Noyember 90. 



6 TUB PRESENT STATE OF THE ROYAL SOCIETY, AXD 

carrying on experimental research, the Transactions of 
the Fellows, recorded by the Society, have, with some 
few exceptions, been performed in their own labora- 
tories, and at their own expense. It is, however, pos- 
sible that experiments of great importance, requiring 
Ainds, which few individuals can command, may be 
suggested ; and it is to be hoped that, on such occa- 
sions, the proposers will not fidl to recur to the Society. 
Government, by the command of our august patrons, 
has always been found ready to assist us, when our in- 
quiries have been connected with objects of national 
interest; and, on inferior occasions, the aid required 
might be afforded by an union of the Fellows, many of 
whom, from their situation in public establishments for 
teaching and difiusing natural knowledge, have oppor- 
tunities of procuring the use of grand and expensive 
apparatus. 

When the Royal Society was instituted, it stood 
alone in Britain; and the associations of learned men 
that were formed soon after, in different parts of the 
empire, for pursuing natural science, were either de- 
pendent or affiliated societies. But, in these latter 
times, the field of knowledge has become so extensive, 
and its objects so various, that separate and independent 
bodies have arisen for registering observations and col- 
lecting facts, each in a different department. It would 
be impossible that our records, as they are now pub- 
lished at our own expense, should contain histories of 
the multi&rious phenomena of all the kingdoms of 
nature, of all the observations made in zoology, botany, 
mineralogy, geology, and practical astronomy. It is 
satisfactory, therefore, to know that institutions exist 
for preserving and publishing such histories in detail. 
I trust that, with these new societies, we shall always 



THE PROGRESS AND PROSPECTS OF SCIENCE. 1 

preserve the most amicable relations, and that we shall 
mutually assist each other; and that they, recollecting 
our grand object, which is to establish principles on in- 
ductive reasoning and experiments, and to make useful 
applications in science, will, should any discoveries be 
made by their members respecting general laws, or im- 
portant facts observed, which seem to lead to purposes 
of direct utility, do us the honour to communicate them 
to us. They will have no dishonourable place in being 
published in those records, which remain monuments of 
all the country has possessed of profound in experi- 
mental research, or ingenious in discovery, or sublime 
in speculative science, from the time of Hooke and 
Newton, to that of Maskelyne and Cavendish. 

I am sure there is no desire in this body to exert 
anything like patriarchal authority, in relation to these 
institutions ; or, indeed, if there were such a desire, it 
could not be gratified. But I trust there may exist in 
the new societies, that feeling of respect and affection 
for the Royal Society, which is due to the eldest 
brother, to the first-born of the same family ; and that 
we shall co-operate, in perfect harmony, for one great 
object which, fi'om its nature, ought to be a bond of 
union and of peace, not merely amongst the philo- 
sophers of the same country, but even amongst those of 
different nations. 

When, by the unrivalled power of one great genius, 
and the industry and talent of his illustrious disciples, 
the laws of the motions of the great masses of matter 
composing the imiverse were discovered, and most of 
the physical phenomena connected with them solved, it 
appeared as if the field of scientific research were ex- 
hausted, as if the rich crops taken from the soil had 
rendered it steril, and that little was left for the inge- 



8 THE PRESENT STATE OF THE ROYAL SOCIETY, AND 

nuity and labour of future inquirers ; time^ however, has 
proved how unfounded was this opinion, and how nearly 
approaching to infinite, are the objects of natural philo- 
sophy. Scarcely has any period of thirty years passed 
without offering a train of important discoveries, and 
every new truth or new fiict has led to new researches ; 
becoming, as it were, a centre of light, from which rays 
have proceeded in different directions, showing to us 
unexpected objects ; so that this kind of knowledge is 
as inexhaustible, as the resources of the human mind ; 
and philosophers, like the early cultivators in a great 
new continent, by every acquisition they make, discover 
new and extensive uncultivated spots beyond. As a 
chart of what is known in lately-discovered regions is 
essential in guiding the traveller to new researches, so, 
in natural knowledge, notices of the limits or boundary 
lines of different new departments of science, and of the 
aspects and characters of novel objects may be useful to 
scientific investigators; I shall, therefore, offer a few 
hints respecting those different departments of inquiiy 
which appear most capable of improvement. 

In pure mathematics : though their nature, as a work 
of inteUectual combination, framed by the highest efforts 
of human intelligence, renders them incapable of re- 
ceiving aids fi*om observations of external phenomena, 
or the invention of new instruments, yet they are at 
this moment abundant in the promise of new applica- 
tions ; and many of the departments of philosophical 
inquiry, which appeared formerly to bear no relation to 
quantity, weight, figure, or number, as I shall more 
particularly mention hereafter, are now brought under 
the dominion of that sublime science, which is, as it 
were, the animating principle of all the other sciences. 

When the boundary of the solar system was enlarged 



THE PROORBSS AND PROSPECTS OF SCIENCE. 9 

by the discovery of the Georgiam Sidos, and the remote 
parts of space accurately examined by more powerful 
instruments than had ever before been constructed^ 
there seemed little probability that new bodies should 
be discovered nearer to our earth than Jupiter ; yet this 
supposition, like most others in which our limited con- 
ceptions are applied to nature^ has been found erro- 
neous. The discoveries of Piazzi, and those astro- 
nomers who have followed him, by proving the existence 
of Ceres, Pallas, Vesta, and Juno — bodies smaller than 
satellites, but in their motions similar to primary planets 
— ^have opened to us new views of the arrangement of 
the solar system. Astronomy is the most ancient, and 
the nearest approaching to perfection, of the sciences ; 
yet, relating to the immensity of the universe, how un- 
bounded are the objects of inquiry it presents I And, 
amongst them, how many grand and abstruse subjects of 
investigation I Such, for instance, as the nature of the 
systems of the fixed stars and their changes, the relar 
tions of cometary bodies to the sun, and the motions of 
those meteors which, in passing through our atmo- 
sphere, throw down showers of stones; for it cannot be 
doubted that they belong to the heavens, and that they 
are not fortuitous or atmospheric formations ; and, in a 
system which is all' harmony, they must be governed by 
fixed laws, and intended for definite purposes. 

The grand question of universal gravitation, and its 
connexion with the figure of the earth, has been long 
solved ; but the mechanical refinements of one of our 
Fellows, have afforded means of estimating, with more 
perfect exactness, the force of gravity : and that pen- 
dulum, which is so well fitted as a standard of measure, 
may be admirably applied in acquainting us with the 
physical constitution of the surfiice of the earth. I trust 

B 5 



10 THE PRESENT STATE OF THE ROYAL SOCIETY, AND 

we fiball have some interesting new experiments on the 
subject. Our brethren of the Royal Academy of 
Sciences of Paris^ who have laboured with so much zeal 
and activity towards the measurement of a great arc of 
the meridian in France and Spain^ are^ I know» ex- 
tremely desirous their measures may be connected with 
those carried on by the command of the Board of Ord- 
nance in Britain, — that the work may be completed by 
the philosophers of both countries. Should this be 
done, there will be estafolishedy on the highest autho- 
rity, an admeasurement of nearly 20 degrees, or -^^th of 
the whole circumference of the earth, from the Shetland 
Islands to Formentera, which will be a great record for 
posterity, and an honour for our own times. 

I cannot pass over the subject of the %ure of the 
earth without referring to the late voyage to the Arctic 
Regions, which has shown that there is an accessible 
sea to the west of Baffin's Bay, presenting hopes of 
other dbcoveries, and which, though unsuccessful in its 
immediate objects, has terminated, nevertheless, in a way 
equally honourable to those by whom the expedition 
was planned, and to the brave, enterprising, and scien- 
tific navigators by whom it was executed. Such expe- 
ditions are worthy of the great maritime nation of the 
world, showing that her resources are not merely em- 
ployed for gaining power or empire, but likewise for 
what men of science must consider as nobler purposes, 
the attempting discoveries which have the common 
benefit of mankind for their object, and the extension 
of the boundaries of sdenee. 

In the theory of light and vision, the researches of 
Huyghens, Newton, and WoUaston, have been followed 
by those of Matus ; and the {^nomena of polarization, 
which we owe to the genius of that excellent and mudi 



THE PROGRESS AND PROSPECTS OF SCIENCE. 11 

to be lamented philosopher^ are constantly leadijsg to 
new discoveries; and^ notwithstanding the important 
labours of Arago, Biot, Brewster^ and Herschel, die 
inquiry is not yet exhausted ; and it is extremely pro- 
bable^ that these beautiful results will lead to a more 
profound knowledge than has hitherto been obtained, 
concerning the intimate constitution of bodies, and 
establish a near connexion between mechanical and 
chemical philosophy. 

The subject of heat, so nearly allied to that of light, 
has lately afforded a rich harvest of discovery ; yet it is 
fertile in unexploied f^ienomena. The question of the 
materiality of heat will probably be solved at the same 
time as that of the undolatory hypothesis of light, if, 
indeed, the human mind should ever be capable of un- 
derstanding the causes of these mysterious phenomena. 
The applications of the doctrine of heat to the atomic 
or corpuscular philosophy of chemistry, abound in new 
views, and probably, at no very distant period, these 
views will assume a {precise mathematical form. There 
are many remarkable circumslanoes which seem to point 
to some general law on the subject : — first, the apparent 
equable motion of radiant matter, as light and heat, 
through space; second, the equable expansion of all 
elastic fluids, by equal increments of temperature ; 
thirds the contraction or expansion of gases, by chemi- 
cal changes, in some direct ratio to their original volume, 
for iiiistance -|^ or ^ ; fourth, the circumstance that the 
elementary particles of all bodies, appear to possess the 
same quantity of heat 

In electricity, the wonderful instrument of Volta, 
has done more for the obscure parts of physics and 
chemistry, than the jxiicroscope ever effected for natural 
history, or even the telescope for astronomy. After 



12 THE PRESBNT STATE OF THE ROTAL SOCIETY, AND 

presenting to us the most extraordinary and unexpected 
results in chemical analysis, it is now throwing a new 
light upon magnetism, 

Snppeditatque noTO confettim lamine lumen. 

But upon this question I shall enter no furtiier, as it 
has been discussed, in the discourse given on the award 
of the Copleian medal to M. CErsted, by my predeces- 
sor in office,* with all his peculiar sagaci^ and happy 
talent of illustration. 

To point out all the objects worthy of inquiry in 
chemistry, would occupy the time appropriated to many 
sittings of the Society. I cannot, however, avoid men- 
tioning, amongst important desiderata, the knowledge 
of the nature of the combinations of that principle 
existing in fluor, or in Derbyshire spar, and which has 
not yet been obtained pure ; the relations of that ex- 
traordinary fact, the metallization of ammonia, and the 
connexion between mechanical and chemical pheno- 
mena, in the action of voltaic electricity. I must con- 
gratulate the Society on the rapid advances made in 
the theory of definite proportions, since it was advanced 
in a distinct form, by the ingenuity of Mr. Dalton. I 
congratulate the Society on its progress, and on the 
promise it afibrds of solving the recondite changes, 
owing to motions of the particles of matter by laws 
depending upon their weight, niunber, and figure, and 
which will be probably found as simple in their origin, 
and as harmonious in their relations, as those which 
direct the motions of the heavenly bodies, and produce 
the beauty and order of the celestial systems. 

The crystallizations, or regular forms of inorganic 
matter, are intimately connected with definite propor- 

• [Dr. Wollaston.] 



THS PROGRESS AND PROSPECTS OF SCIBXCB. 13 

tioiis, and depend upon the nature of the combinationB 
of the elementary particles ; and both the laws of elec- 
trical polarity^ and the polarization of light, seem re- 
lated to these phenomena. As to the origin of the 
primary arrangement of the crystalline matter of the 
globe, various hypotheses have been applied, and the 
question is still agitated, and is perhaps above the pre- 
sent state of our knowledge ; but there are two princi- 
pal fiicts which present analof^es on the subject, one, 
that the form of the earth is that which would result, 
supposing it to have been originally fluid ; and the other, 
that in lavas, masses decide^y of igneous origin, crys- 
talline substances, similar to those belonging to the 
primary rocks, are found in abundance. 

In following the sensible phenomena of nature, from 
the motions of the great masses of the heavenly bodies 
which first impress the senses and afiect the imaginar- 
tion, to the changes individually imperceptible, which 
produce the results of crystallization, there is a regular 
gradation, and a series conformable to analogy; and 
where crystallization ends, another series, that of ani- 
mated nature, begins, governed by a distinct set of 
laws, but obedient to a principle, the properties of 
which, independent of matter, can never be submitted 
to human observation. The functions and operations 
of oiganized beings, however, offer an infinite variety 
of beautiful and important objects of investigation. 
For instance, in those refined chemical processes, by 
which the death and decay of one species afford nourish- 
ment to another and higher order, by which the water 
and inert matter of the soil and the atmosphere are con- 
verted into delicately-organized structures, filled with 
li& and beauty. In vegetable physiology, how many 
phenomena still remain for investigation I the motion 



U THS PRESENT STATE OF THE ROYAL SOCIETY, AND 

of the sap, the fiinctions of the leaves, for instaace, and 
the nature of the organs of assimilation. In animal 
physiology, the subjects are still more varied, more 
obscure, and of a higher character. May we not hope 
those philosophers of the schools of Grew and Hunter, 
who have already done so much for us, will not cease 
their efforts for the improvement of these branches of 
science, whidi are not merely important in their philo- 
sophical relations, but of great utility, the one to agri- 
culture, the other to medicine ? 

Gentlemen, to conclude, I trust in all our researches 
we shall be guided by that spirit of philosophy, awaken- 
ed by our great mastery Bacon and Newton; that sober 
and cautious method of inductive reasoning which is 
the germ of truth and of permanency in all the sciences. 
I trust that those amongst us who are so fortunate as to 
kindle the light of new discoveries, will^use them, not 
for the purpose of dazzling the organs of our iatellec- 
tual vision, but rather to enlighten us, by showing 
objects in their true forms and colours ; that our philo- 
soj^ers will attach no importance to hypotheses, except 
as leading to the research after facts so as to be able to 
discard or adopt them at pleasure, treating them rather 
as parts of the scaffolding of the building of science, 
than as belonging either to its foundations, materials, 
or ornaments ; that they will look, where it be possible, 
to practical applications in science, not, however, for- 
getting the dignity of their pursuit, the nobl^t end of 
which is, to exalt the powers of the human mind, and 
to increase the sphere of intellectual enjoyment, by 
enlarging our views of nature, and of the power, 
wisdom, and goodness of the Author of nature. 

Gentlemen, the Society has a right to expect from 
those amongst its Fellows, gifted with adequate talents, 



THE PROGRESS AND PROSPECTS OF SCIENCE. 15 

who have not yet laboured for science^ some proofi of 
their zeal in promoting its progress ; and it will always 
consider the success of those who have ahready been 
contributors to our volumes, as a pledge of future 
labours. 

For myself, I can only say, that I shall be most happy 
to give in any way assistance, either by advice or ex- 
periments, in promoting the progress of discovery. 
And though your good opinion has, as it were, honoured 
me with a rank similar to that of general, I shall be 
always happy to act as a private soldier in the ranks of 
science. 

Let us then labour together, and steadily endeavour 
to gain what are perhaps the noblest objects of ambition 
-^acquisidons which may be useful to our fellow-crea- 
tures. Let it not be said, that, at a period when our 
empire was at its bluest pitch of greatness, the sciences 
began to decline ; let us rather hope that posterity will 
find, in the Philosophical Transactions of our days, 
proofs that we were not unworthy of the times in which 
we lived. 



16 



DISCOURSE OF TEE PRESIDENT, 
NoTBXBBB 30th, 1821, 
In announeiDg the Award of two Medals on Sir Godfbby Coplbt's 
Donation. One to J. W. F. Hbkbchbl, Esq., F.R.S., for his yarious 
Papers on Mathematical and Physico-Mathematical Subjects, pub- 
lished in the Philosophical Transactions. And the other to Captain 
EowABO Sabinb, R.A., for his Papers containing an Account of 
his Yarions Experiments and Observationsy made daring the Voyage 
and Expedition in the Arctic Regions. 

Gentlemen^ 
The progress of discovery, even when belonging to 
past times or to distant coontries, is always an agreeable 
subject of contemplation to philosophical men ; but the 
pleasure derived fix>m it is much higher when it arises 
from the exertions of the talents of our own country* 
men, when it originates in our own body, and when 
there is the power, not only of acknowledging and 
rejoicing at it, but likewise of distinguishing the persons 
to whom it is owing by a permanent mark of respect. 
You will therefore, I am sure. Gentlemen, have as much 
satis&ction in hearing, as I have in slating, the decision 
of the council of the Royal Society, in the award of 
two of your Copley medals, — one of this year, and 
one not disposed of on a former occasion, — to two 
of our worthy Fellows, whose papers have been pub- 
lished in the Fhilasaphical Transactions, and whose 
merits have been for some time known to you, — John 
Frederick William Herschel, Esquire, and Captain 
Edward Sabine, of the Royal Artillery. I shall ask 
your attention for a short time, Gentlemen, whilst 



THE AWABB OF THB COPLEY MEDALS. 17 

I state the grounds of the decision of your council, 
and I shall begin with the labours of Mr. HerscheL 

There is certainly no branch of science so calculated 
to awaken our admiration as the sublime or transcen- 
dental geometry, not only as showing the wonderful 
powers and resources of the human mind, but likewise 
demonstrating the wisdom and beauty of the laws 
of the system of the universe. It is, perhaps, the 
highest triumph of human intelligence, that, proceeding 
from the consideration of mere unities or points, lines, 
or surfaces, it should, by gradual generalizations, sub- 
stitutions, and abstractions, be able to arrive, not only 
at the knowledge of all possible conditions of number 
and quantity, but likewise of time and motion ; and by 
employing its own pure intellectual creations, to anti- 
cipate the results of observation and experiment, and 
determine the movements, not only of the bodies 
which form permanent parts of our system, but likewise 
of those which seem only occasionally to visit it, and 
which belong, as it were, to the immensity of space. 

Whether the importance of the subject be con- 
sidered, or the glory that has been derived by the 
society from the labours of those amongst its members 
who have cultivated the higher branches of the mathe- 
matics, it must be very gratifying to you to hear that 
Mr. Herschel, after gaining, at a very early period of 
life, academical honours of the highest kind in that 
university where the exact sciences are most pro- 
foundly studied, has successfiilly continued his pursuit 
of this kind of knowledge: and not contented with 
understanding and illustrating the most elaborate works 
of his predecessors and contemporaries, has made ad- 
ditions to them, and that even in the most abstruse and 
di£Scnlt branches of analysis. 



18 THE AWARP OF THE COPLEY MEDALS 

Four papers of Mr. Herschel^ on pure mathematical 
subjects^ are to be found in your Transactions, The 
first, on a remarkable application of Cotes's theorem. 
The second^ on the consideration of various parts 
of analysis, in which he has examined one of the most 
sublime points of the doctrine of fluxions, the calculus 
of generating functions, and makes a new application 
of them to the case of logarithmic transcendents, and 
derives firom them the summation of one of the most 
important series which has ever received discussion. 
The third paper is on the development of exponential 
functions, together with several new theorems relating 
to finite difierences. The fourth paper is on circulating 
fimctions, and the integration of a class of finite dif- 
ferences into which they enter as co-efficients. 

I cannot attempt an analysis of these papers ; that 
their merits may be understood, they must be deeply 
studied; and, by the best mathematicians, they are 
regarded as ingenious and profound. 

The author, in treating of algebraical or fluxional 
instruments, as they may be called, of the relations of 
variable quantities or functions which may be supposed 
capable of indefinite diminution or increase, has in* 
dulged in no vague metaphysical abstractions. He has 
shown a great love of simplicity in his processes, ap- 
pearing rather desirous of being intelligible and useful, 
than anxious to display the variety and extent of his 
acquisitions. In all these papers Mr. Herschel has 
proved himself intimately acquainted with the works of 
the great masters of analysis, and has exhibited equal 
powers of seizing particular applications of methods 
already known, and of developing new and general 
views ; thus demonstrating himself the worthy associate 
of a Brinkley, a Woodhouse, an Ivory, and a Young, 



TO MB. HERSCHEL AND CAPTAIN SABINE. 19 

who Iiave^ in late times, travelled, with so much zeal 
and success, towards mathematical discoveries, in these 
noble paths of investigation opened by the unrivalled 
genius of Newton, and too long deserted by our 
countiymen, and occupied, ahnost exclusively, by 
illustrious foreigners. 

But Mr. Herschel has not limited himself to the 
invention or development of formulae, to what may be 
called the construction of the instruments of the 
science of quantity, he has made important applications 
of them, which is perhaps the highest claim that can 
be made to the approbation of this Society ; for though, 
as a mere exercise, the higher mathematics strengthen 
the reasoning faculties, and afford intellectual pleasure, 
yet it is by enabling us to solve the physical phenomena 
of the universe, and modify the properties of matter, 
that they have their grandest end and use. In these 
respects, they are really power ; and they may be com- 
pared to that power which we witness in the vapour of 
water, which, passing into the free atmosphere, exhibits 
only a pleasing spectacle ; but which applied in the 
steam-engine, becomes the moving principle of the 
most useful and extensive machinery, and the source of 
the most important arts of life. 

There are two papers of Mr. Herschel's, in the last 
volume of the Dransactions, on physico-mathematical 
subjects, and both of them connected with optical phe- 
nomena. All the Fellows must be acquainted with the 
beautiful discoveries of Malus, of that peculiar modifi- 
cation given to rays or particles of light, by their pas- 
sage through certain transparent bodies, or by their 
reflection from certain surfaces, which has been called 
polarization ; and the ingenious and elaborate researches 
of Biot, Arago, and Brewster, in consequence of the 



20 THE AWARD OF THE COPLEY MEDALS 

discovety^ have been illustrated from this chair by your 
venerable and illustriouB deceased President But^ 
notwithstanding the talents and industry of these dis- 
tinguished philosophers, Mr. Herschel has been able to 
add to the subject some novel investigations ; and, in 
reasoning upon the tints developed by polarized light, 
has reduced the explanation of the phenomena to one 
general fact — ^namely, that the axes of double refraction 
differ in their position in the same crystal^ for the dif- 
ferent-coloured rays of the spectrum, and that this ele- 
ment must enter into all rigorous formulse of double 
refraction; and, consequendy, that the idea of the 
colours of thin plates being correspondent with the 
tints developed by polarized light, is not conformable 
to the facts. 

Though it appears that some similar observations 
were made by one of the philosophers just mentioned, 
without the knowledge of what Mr. Herschel had done, 
yet the latter has unquestionably the priority : and it is 
agreeable to find a harmonious coincidence between two 
accurate reasoners and acute observers. 

In this paper Mr. Herschel has extended or modified 
the discoveries of others : the second is more original, 
and on a subject highly important in practical objects. 

With the view of enabling artists to substitute, in 
working their glasses, certain mathematical rules for 
empirical methods, Mr. Herschel has presented, under a 
general and uniform analysis, the whole theory of the 
aberration of spherical surfaces, and has furnished 
simple tabular rules, by which the workmen may adapt 
their tools to the object required, in forming glasses for 
the telescope; thus adding to the immense obligations 
owing to the name of Herschel, in every thing connected 



TO MB. HER8CHEL AND CAPTAIN SABINE. 21 

with the progress of modem astronomy^ and the know- 
Ik^ of celestial phenomena. 

Convinced, Grentlemen, that you approTC of the de- 
cision of your Council, I shall present this medal, en- 
graved with his name and the date of the year, to Mr. 
HerscheL 

Mb. Hebschbl, 
Receive this medal. Sir, as a mark of our respect 
and of our admiration of those talents which you have 
applied with so much zeal and success, and preserve it 
as a pledge of future exertions in the cause of science, 
and of the Royal Society ; and, believe me, you can 
communicate your labours to no public body by whom 
they will be better received, or through whose records 
they will be better known to the philosophical world. 
You are in the prime of life, in the beginning of your 
career, and you have powers and acquirements capable 
of illustrating and extending every branch of physical 
inquiry ; and, in the field of science, how many are the 
spots not yet cultivated t Where the laws of sensible 
become connected with those of insensible motions, tiie 
mechanical with the chemical phenomena, how littie is 
known I In electricity, magnetism, in the relations of 
crystallized forms to the weights of the elements of 
bodies, what a number of curious and important objects 
of research I And they are objects which you are pe- 
culiarly qualified to pursue and illustrate. 

May you continue to devote yourself to philosophical 
pursuits, and to exalt your reputation, already so high, 

** Yirtntem extendere fkctb ." 

And these pursuits you will find not only glorious but 
dignified, usefiil, and gratifying in every period of life : 



22 THE AWARD OF THE COPLEY MEDALS 

this, indeed, you must know best in the example of 
your illustrious fitther, who, full of years and of hononiv, 
must view your exertions with infinite pkasure ; and 
who, in the hopes that his own imperishable name will 
be permanently connected with yours in the annals of 
philosophy, must look forward to a double immortality. 

I shall now speak of the researches of Captain Sabine. 

You will. Gentlemen, I am sure, anticipate the 
grounds of the decision of your Council, in awarding to 
him the other medal. 

The expeditions to the Arctic Regions, which have 
been planned with so much liberality of view by the 
Admiralty, and which are canying on with so much 
skill, perseverance, and courage by the brave officers 
and seamen concerned in them, have awakened so 
strong an interest in the public mind, and are so well 
known in the printed details, that it is almost unneces- 
sary to point out the particular merits of the most dis- 
tinguished amongst those bold and enterprising persons 
who have thus <levoted themselves to the cause of 
science and their country. Yet, Captain Sabine having 
been appointed, in consequence of the recommendation 
of the Council of the Royal Society, astronomer and 
philosophical observer to the two first of tibe expedi- 
tions, and having more than answered dieir recommen- 
dation, they have thought it right to express their sense 
of his high merits, by the vote I am now announcing. 

Ciq[>tain Sabine had been for some time known as an 
active officer, and by his labours in these expeditions, 
he has proved himself worthy the name of an accurate 
philosophical observer: he has shown great industry 
and perseverance in making his experiments, under cir- 
cumstances when they were peculiarly difficult, and has 



TO MB. HEBSCHEL AND CAPTAIN SABINE. 23 

aocumolated an immense number of observations in 
astronomy and meteorology^ and on tbe phenomena of 
magnetism and gravitation. 

Active courage^ Gentlemen, is a quality so inherent in 
eveiy Briton, and so nobly displayed in our naval and 
military triumphs, that it is scarcely necessary to pndse 
it; but, there is a fortitude and a patience in enduring 
hardships, and in bearing privations, which may be con* 
sideied as rarer qualities, and whidi demand our 
highest commendation. The place, as you know, 
where Captain Sabine conducted his principal experi- 
ments was on the ice of the Polar Sea, whare the vessel 
was for several months frozen tip. During a con- 
siderable portion of the time, he was in darkness, 
or only guided by a very doubtful twilig^ ; and such 
was the intensity of the cold, that exposure, even in 
the warmest clothing, to the atmosphere for any time, 
was always painful, and sometimes dangerous. It was 
impossiUe to touch the metallic instruments with the 
naked hand, without being frost-bitteti ; and such was 
the temperature of this inclement spot, probably as 
cold as any belonging to the northern hemisphere, that 
the artificial hcnizon of mercury became frozen during 
an observation ; yet Captain Sabine's experiments seem 
to have been conducted with as much care and pre- 
cision, as if he had been possessed of the conveniences 
and luxuries of a royal observatoiy, and the advantages 
and repose of the happiest climate and situation. 

Three of his papers have been published in your 
Transactions : the two first contain observations re- 
lating to magnetic phenomena, such as, tbe influence 
of the iron in the ship, upon the correctness of results 
obtained by the compass, and the intensity and 
▼ariaticm of the magnetic force in approaching the 



24 THE AWARD OF THE COPLEY MEDALS 

magnetic pole, which last are given in a series of tables. 
The other paper is more important, containing an ac- 
count of experiments on the vibrations of the pendulum^ 
in different latitudes. 

On the subject of this paper, I shall enter into a few 
details. The invention of the pendulum, by Galilseo 
Galilaei, is placed beyond all doubt; and that this il- 
lustrious philosopher endeavoured to apply it as a 
measure of time, and that his son, Vincenzo Galilaei 
constructed the first pendulum clock at Venice, 1649, 
is proved, both by manuscript documents that I have 
seen at Florence, and by the printed testimonies of the 
Academia del Cimento ; but the great principle of the 
instrument, in its application to clock-work, it is well 
known, is ovring to the illustrious Huyghens, who dis- 
covered that the vibrations were isochronous, when per- 
formed in cycloidal arcs. 

It is not certain by whom the pendulum was first [no- 
posed as an universal standard of measure, but it is 
hardly likely that such an application of it should have 
escaped the sagacity of the Dutch philosopher ; yet, as 
early as 1661, Lord Brouncker, after mathematically 
demonstrating the properties of the pendulum, by a very 
elaborate analysis, brought in a paper to the Royal 
Society on a common measure, and Sir William Petty, 
at the same meeting, proposed to make experiments, for 
this purpose, on the vibrations of the pendulum, and Sir 
Christopher, then Doctor, Wren, was desired to think 
of some other common measure, and he proposed, on 
his return firom Oxford, a certain part of the length of 
a degree upon the earth. Various experiments, like* 
wise, seem to have been made by different members of 
the Royal Society, between 1661 and 1664, on the 
times of the vibrations of pendulums of different lengths, 



TO MR. HERSCHBL AND CAPTAIN SABINB. 25 

as Standards of measure ; and Huyghens did not pro- 
pose the pendulum vibrating seconds, as an universal 
standard, till the end of this year, November, 1664 ; 
and that, in a letter to the Royal Society, but the pro- 
position is given in a very precise and beautiiiil form. 

When the calculations of Newton and Huyghens, and 
the experiments of Richer, had proved that the vibra- 
tions of the same pendulum were not performed in the 
same time in different latitudes, M. de la Condamine 
proposed, and endeavoured to establish, the length of 
the pendulum vibrating seconds at the equator, as a 
common standard. But in no part of Europe was this 
standard adopted ; and the French metre, as you well 
know, is founded upon the measure by triangulation, 
made by some distinguished members of the Institute, 
of a small arc of the meridian. 

It is to the scientific zeal and enlightened views of 
our worthy treasurer, Mr. Gilbert, that the elaborate in- 
vestigation of the properties of a pendulum, as an uni- 
versal standard of measure, is owing. By making it a 
question of national importance in Parliament, he di- 
rected all the scientific talents and resources of the coun- 
try to the object ; and the invariable pendulum, con- 
trived with such a happy spirit of invention, and ex- 
amined with such unceasing activity and minute accu- 
racy by Captain Kater, was the fortunate result. 

The experiments made with this beautiful instru- 
ment, by the inventor, are well known to you, having 
been published at full length in your Transactions. 
Captain Kater*s results proved that it was a most deli- 
cate measure of gravity, not only for the whole earth, 
but likewise as even marking the density of particular 
parts of the surface; and his conclusions rendered it 
very denrable, that the length of the pendulum, or, 

YOU vn. 



26 THE AWARD OF THE COPLEY MEDALS 

what is tantamount, the number of its vibrations, should 
be determined as extensively as possible, from the Polar 
to the Equatorial Regions. 

A happy opportunity occurred, with respect to the 
Arctic Pole, in the two late expeditions ; and Captain 
Sabine, being provided with the necessary means, ap- 
plied them with all possible accuracy and industry, as the 
details of his paper prove; and in north latitude of 
nearly 74^ degrees, the extreme point of his observa- 
tions, he has shown the length of the pendulum vibrat- 
ing seconds, to be 39*207 inches, and the mean of his 
experiments gives the compression of the earth, at the 
Pole, as ^^-y. 

Captain Sabine did not accompany the third expedi- 
tion, because he conceived that he had effected all that 
he was capable of performing with the pendulum in 
north latitudes, which was the great object of his re- 
searches in the two former voyages ; and his scientific 
ardour made him resolve to endeavour to complete his 
investigation even to the Line ; and it is in consequence 
of his carrying this resolution into effect, that he is not 
now present to witness the strong interest you have 
taken in his pursuits. Having braved the long night, 
and almost perpetual winter of the Polar Regions, he is 
gone, with the same laudable object, to expose himself 
to the burning sun and constant summer of the Equator. 

Should Providence bestow on him health and a suc- 
cessful voyage, I have no doubt he will return to us wiA 
a valuable collection of facts and observations. He has 
carried with him instruments of various kinds for mak- 
ing researches, — ^as to the temperature and currents of 
the ocean, — the effects of heat and light, — the state of 
the atmosphere, — and other objects connected with the 
natural history of the globe. And his researches on the 



TO MB. HERSCHEL AND CAPTAIN SABINE« 27 

pendulum, combined with those Captain Kater has 
made in our own island, and others carrying on at the 
observatory established at the Cape of Good Hope, and 
by Sir Thomas Brisbane in New South Wales, will, I 
have no doubt, furnish a mass of information, from 
which the figure of the earth may be deduced with much 
more accuracy, than from any preceding experiments 
or deductions. And as the Royal Sodety, through its 
most illustrious member, had the honour of publishing 
to Europe, more than a century ago, the grand theore- 
tical principles of this discovery, may we not hope that 
its present Fellows will give it all the practical elucida- 
tions of which it is susceptible ? 

Captain Sabine not being present. Gentlemen, for the 
reasons I have stated, I shall deliver the medal to his 
firiend and brother. 

Me. Sabine, 
In informing Caiptain Sabine of what has taken place 
this day, you will, I trusty state to him our deep sense of 
his merits. His knowledge of this expression of our 
opinion may, perhaps, animate him during the difficult 
enterprise he has undertaken ; for he has already shown 
how highly he values the praise of the Royal Society, 
which, vrith the good opinion of his countrymen, has 
been hitherto the only reward of his labours. Assure 
him how strongly we feel his disinterestedness and ge- 
nuine love of science, and that our constant vrishes are 
expressed for his safe return, and for the successful ac- 
complishment of all the objects of his voyage, which 
will ensure, even to him, additional claims upon the 
gratitude of all lovers of science. 

c2 



28 



DISCOURSE OF THS PRESIDENT, 

AHNZYBaSAAT, NOY. 90THy 1828, 

On the Chancten of some DeceiMd Fellowg ; Sir Hbnkt C. Englb* 
FIELD, Bart, Sir William Herscbbl, Dr. Marcet, the Rev. 
Samubl ViiTCB, Dr. Pabrt, Dr. Carmichael Smith, HM. 
Haut, Dblambrb, and Bbrthollbt. — And on the Award of the 
Medal on Sir Oodfrbt Coplbt's Donation, to the Rer. Professor 
BucKLAND, for his Paper on the Bones of Hyssnas, and other 
Animals found in a Care at Kirkdale, in Yorkshire. — ^With General 
Views on the Progress and Prospects of Geology. 

Ix perusing this Ust (of deaths). Gentlemen, some names 
have arrested my attention, ^ith respect to which, 
I consider it as a duty to say a few words. I cannot 
enter upon a studied eulogy of the illustrious dead ;* but 
I am sure you will not consider a short tribute of 

* [The Author's brief eulogies of the illustrious dead in these Discourses 
were given with the warmth of love and gratitude for scientific worth, with- 
out cavil and without disparagement ; they display the nobler qualities 
and higher merits of the indiyiduals, without exposing to the world's 
scorn their infirmities. This I mention, reflecting with regret, on a 
contrary procedure of late, relating to men of the loftiest attainmentt, 
including even Newton (vide Quarterly Review, No. CIX.), nowise for 
the interest and glory of science; and which, even if unfounded, will 
give a handle to the low and worldly minded to scoff at the influence or 
want of influence of science on the moral mind, and to call in question 
the noble maxim " that wisdom is Justified of her children." Let us not 
foiget the cune of Noah on his youngest son, and his blessing on the 
elder sons, who with affectionate respect approached him with inverted 
faces not to see the nakedness they came to cover; an incident deserv- 
ing of a place, in its allegorical bearing in the sapientia veterumy and 
which, it may well be imagined, Beoon would have applied, m a maaterly 
manner, to the younger sons of science.] 



CHARACTSBS OF SOME DBCEAS£D FELLOWS. 29 

respect to their memory, such as naturally arises out of 
this occasion, improper or out ^of place ; and which, 
however unequal it may be to their merits, will, I trust, 
be in unison with the feelings of the Society. 

Sir Henry Englefield, the first person whom I shall 
mention, was known to you as an accomplished gentle- 
man, gifted with a great variety of knowledge, which 
he was always ready to conmiunicate* He had fol- 
lowed astronomy much as an amusement, and some- 
times as a study ; and his early work on comets displays 
considerable research, and a minute acquaintance with 
his subject Though his scientific acquisitions were 
very general, they were, nevertheless, accurate ; and he 
has produced good papers on several different subjects 
of experimental research. He was a clear writer, and a 
learned antiquarian, a liberal collector, and a judge of 
works of art In conversation he was ready and fluent, 
amiable and discursive ; and he will long be regretted 
as an entertaining companion, a warm and excellent 
fiiend, a truly honest man, and an ornament to the 
claas of society in which he moved. 

On the labours and discoveries of Sir William Her- 
schel, it is unnecessary to dwell; they have so much 
contributed to the progress of modem astronomy, that 
his name will probably live as long as the inhabitants of 
this earth are permitted to view the solar system, or to 
understand the laws of its motions. The world of 
adence — ^the civilized world, are alike indebted to him 
who enlarges the boundaries of human knowledge, who 
increases the scope of intellectual enjoyment, and 
exhibits the human mind in possession of new and un- 
known powers, by which it gains, as it were, new 



30 CHARACTERS OF 80MB DECEASED FELLOWS. 

dominions in space; acquisitions which are imperiah« 
able ; not like the boundaries of terrestrial states and 
kingdoms, or eren the great monuments of art, which 
however extensive or splendid, must decay ; but secured 
hy the grandest forms and objects of nature, and re- 
gistered amongst her laws. 

The acuteness and accuracy of Sir William Heischel^ 
as an astronomical observer, are demonstrated by his 
discovery of a new planetary system, and of a number 
of satellites before unknown. His genius for specula- 
tion, and his powers of inductive reasoning, are il- 
lustrated by his views of the stars and nebulae, com^ 
posing what we know of the system of the universe ; 
and his talents for physical research are sho¥m by his 
important discovery of invisible rays in the solar 
spectrum. 

The moral qualities of this celebrated man are so 
well known, that I shall barely touch upon them. 
Raised entirely by his own merits, and by the powers 
of his own intellect, to the station he occupied in the 
world of science, honoured by the patronage and kind- 
ness of a most beneficent sovereign, he was spoiled 
neither by glory nor by fortune, and always retained 
the native simplicity of his mind. In all his domestic 
and social relations, he was most amiable. As his life 
had been useful and honourable, so was his death 
happy : and he had little left to wish for, except that 
expansion of intellect which can only belong to the 
mind in a higher state of existence. Every year of his 
life was distinguished by some acquisition or blessing ; 
and when age no longer permitted him to make dis- 
coveries he saw his son taking his place, and dis- 
tinguishing himself in the same career. 

If the scientific world in general have cause to r^ret 



CHARACTBRS OF SOMB BXCBASEB FELLOWS. 31 

the loss of Sir William Herschel, and to reverence his 
memory, the Royal Society, in particular, has a deeper 
seoae of sorrow, and a higher motive for veneration. 
All his important papers were published in your Trans- 
actions ; and no name in modem times has more con- 
tributed to your glory. 

Sir William Herschel died at the advanced age 
of eighty-three ; Sir Henry Englefield was seventy ; 
but Doctor Marcet, another of your worthy deceased 
Fellows, had not much passed fifty years; and his 
death was most unexpected and deeply to be lamented, 
He was but a short time before apparently in excellent 
health and spirits, and active in body and mind. Cirr 
cumstances of a happy kind likewise enabled him to 
devote himself ei^tirely to science; and his different 
papers, published in the Transactions, on chemical 
subjects, show how capable he was of sound reasoning, 
accurate experiments, and iqgeuious views, in this 
department of spience ; and^ I doubt not, had his life 
been spared, it would have been devoted to laudable 
scientific objects, A more apaiable in^n thfm Pr. 
Marcet, I believe, never lived. There was a simple 
dignity in his character which commanded reppect; 
and a warmth of manner, arising from a warmth of 
heart, which ensured affection. But why should I dwell 
upon moral and social qualities, which all those who 
knew him must feel, and which I can never describe 
with sufficient truth to give an idea of, to those who 
did not know him ? 

The Rev, Samuel Vince, Plumian Professor of Astro- 
nomy and Experimental Philosophy, in the University 
of Cambridge, was, Uke Sir William Herschel, a man 
who rose to distinction entirely by the exertion of his 



32 CHARACTEBS OF 80MS DBCBASED FELLOWS. 

own talents. He was well known to you as a profouncl 
mathematician, and a clear elementary writer. It is 
enough to say of him, that he was distinguished in tbe 
great mathematical school of this country, and that vee 
are now profiting by the labours and profound acquisi- 
tions of his scholars. 

I shall mention Dr. Parry only as an enlightened 
and ingenious physician, and an amiable and accom- 
plished man ; and Dr. Carmichael Smith, as bar- 
ing received a parliamentary reward for the appli- 
cation of nitrous acid vapour in destroying contagious 
matter. 

On our foreign lisl^ the first name that occurs is the 
Abbe Hauy, who was known as a good natural philoso- 
pher, and whose reputation will pass down to posterity 
on account of his work on crystallography, in which he 
has endeavoured to make the crystalline form of mineral 
bodies, the important character of their classification ; 
and who, in his application of this principle, agisted by 
chemistry, either produced or prepared the way for 
some remarkable discoveries. 

The next is M. Delambre, Secretary to the Royal 
Academy of Sciences at Paris ; an excellent astronomer, 
whose work on the History of Astronomy is a model of 
this kind of composition ; he was distinguished by many 
accurate labours in his favourite science: but his 
greatest experimental work was that which he made 
in conjunction vnth Mechain, the measurement of an 
arc of the meridian in France. He was a good classical 
scholar, an elegant and impartial writer ; and his Dis- 
courses to the Institute, on the annual progress of 



AWARD OF THE COPLEY MEDAL. 33 

science, are marked by good taste, candour, a love of 
justice, and a truly philosophical spirit. 

Berthollet' might be considered the patriarch of 
modem chemistry — ^the friend and companion of Lavoi* 
sier, and Guyton de Morveau, He had contributed 
much to the establishment of that view of the combina- 
tions of oxygen, which has been called the anti-phlo- 
gistic system; and took a part in framing the new 
nomenclature. His principal discovery was that of the 
composition of ammonia, but he was the author of many 
excellent papers on chemical subjects; and the most 
celebrated French chemists now alive were his pupils. 
He was an excellent logician and a good experimenter ; 
and remarkable for a high degree of candour, renounc* 
ing his opinions with the greatest readiness, whenever 
the progress of science was opposed to them ; and this 
even in old age. He was amiable and unaffected, and 
the liberal patron of rising genius wherever it appeared; 
and made a point, even in the bosom of the Academy of 
Sciences, of doing justice to foreigners. 



COPLEY MEDAL. 

The duty I have now to perform, I consider as the 
most gratifying belonging to the office of your Presi- 
dent. It is to announce to you. Gentlemen, the de- 
cision of your council, in awajxiing the medal of the 
Society, for the year 1822, on Sir Godfrey Copley's 
donation, to the Reverend William Buckland, your 
worthy Fellow, and professor of geology in the Univer* 
sity of Oxford, for his account of the fossil teeth and 
bones, discovered in a cave near Kirkdale, in Yorkshire, 

c5 



34 AWARD OF THE COPLEY MEDAL 

and published in the Philosophical Transaction for the 
present year. 

This is the first time that a communication on a sub- 
ject of pure geology has been honoured with bo dis- 
tinguished a mark of approbation ; and from the merits 
of the communication, which has been for some time 
before the public, I am convinced you will think your 
council has performed an act of justice, and not of 
favour, towards the author. 

It is not a little remarkable, that whilst the natural 
history of the heavenly bodies, so fiir removed fix>m us, 
was the earliest object of scientific research, the mineral 
philosophy of the earth we inhabit, of the substances 
under our feet, has been the latest. The brilliancy of 
the celestial phenomena, their connexion widi the 
seasons, and with the superstitions of the ancients; the 
facility with which mathematics were applied to their 
figures and motions, and their relations to time, ren* 
dered astronomy, in all ages and countries, a popular 
study ; whereas the difficulty of penetrating into the 
strata of the surfiice of the globe, the apparent disorder 
and confiision of their contents, and the want of any 
scientific principles applicable to the subject, for a long 
while prevented geology from being numbered even 
among the sciences. 

By the ancients, cosmogonies or dreams vei^)ectang 
the origin and changes of our pliM^ets, were substituted 
for actual observation ; and though, in the early pro- 
gress of general philosophical inquiries in Europe, par- 
ticularly amongst die works of early Members of this 
Society, or contributors to the Transactions, such as 
Hooke, Lister, Holloway, Pococke, and Strachey, some 
general views were formed, and accurate histories of 
particular phenomena recorded; yet it is only within 



TO THE RSY. BR. BUCKLAND. 35 

the last half-century that the subject has been pursued, 
in the active spirit of research, by truly philosophical 
miiuis ; and th^t it has been an object of geaeral scien- 
tific attention* 

At the beginning of this period, mineralogy offered 
a r^uiar arrangemeQt of fossil substances; and De 
Saussure, Pallas, and, above all, Werner, considering 
and. perfectiog it as the alphabet of geology, endea- 
voured to read^ slowly and carefully, this interesting part 
of the Book of Nature. Chemistry, annually making 
a rapid progress, had not only expl^ned the intimate 
nature of mineral bodies, and so affi)rded correct means 
of classing them, but likewise offered the powers of 
judging of their past changes, by analyses deduced from 
accurate experiments ; and the comparative anatomy of 
plants and animals, in tracing and fixing the resem- 
blances betwe^i existing beings, had furnished the links 
of inductive reasoning, by which the extinct species 
belonging to the mineral kingdom were to be ex^unined 
and known. 

Under such advantages it was to be expected that a 
rapid advance would be made in the science. Private 
and public museums have been formed in every part of 
Europe. Societies have been instituted for the express 
purpose of pursoing ^ological inquiry. Maps, in 
which the minejral history of districts and countries is 
laid down, have been published ; and within the last 
twenty years, it is not perhaps unjust to say, that 
rational geology has made more progress than in all the 
pre^cediog ti,me. 

In a discourse so limited in its object as that I am 
now delivering, it would be impossible to mention, even 
in the most cursory mwioer, the labours of those in« 
quirers who have been most successful in this field of 



36 AWARD OF THE COPLEY MEDAL 

science; but no one amongst them has been more 
distinguished^ by ardour in the pursuit of knowled^^e, 
by success in geological discovery, and soundness in 
philosophical reasoning, than Mr. Buckland. His leo 
tures, in the University of Oxford, have raised a 
numerous class of disciples, who are following his 
praiseworthy example in the pursuit of science ; and 
his former publications equally proved his indefatigable 
spirit of research, his accuracy of observation, and his 
caution and sagacity in drawing conclusions. 

Upon the nature of the paper which your council 
has considered as entitling him to the medal, I shall 
make a few observations. It has been probably read 
with interest by every one who is here present ; I will 
not, therefore, attempt to analyse the details. I shall 
merely point out the particular fact that it establishes 
in the history of the globe, and which I consider as of 
great importance ; but for this purpose it will be neces-^ 
sary to offer a few preliminary observations on the 
structure of the known part of our globe, and of the 
changes which it has undergone. 

It has been ascertained, by the examination of a 
great extent of the surface, that the rocks which rise 
to the greatest elevation in the atmosphere, and those 
found at the lowest depths to which human industry 
has, as yet, penetrated, are composed wholly of crystal- 
line matter, containing no remains of organized beings, 
or of any former order of things : upon these rocks, at 
common heights or depths, are found others, principally 
constituted of crystalline matter, and affording some 
few remains of shells, fishes, and plants. To these 
succeed a number of strata, or layers, less consoli- 
dated, affording much smaller proportions of crystals, 
abounding in fragments of the older rocks, and con- 



TO THE REV. DR, BXTCKLAND. 37 

taining imbedded in them, the remains of plants, shells, 
fishes, oviparous reptiles, amphibia, and birds; each 
stratum being characterised by the peculiarity of its 
organized remains. 

Upon these consolidated and extensive strata arc 
found others, which, when not produced by deposition 
of gypsum, in what may be called fresh-water forma- 
tions, consist of clay, sand, gravel, or water^wom stones, 
and in these are discovered, amongst a vast number of 
other deposites, the remains of viviparous quadrupeds. 

In the lowest strata, it has been observed, and I have 
found by experiments, these organized remains con- 
tain none of their original bony matter ; but, in pro- 
portion as the formations or depositions may be sup- 
posed to be more recent, so in proportion is more of 
the original matter of the bone or shell found in them. 
The aremains of the bones of the animals of the saurus 
or lizard kind, found in the limestone of Sussex or 
Dorsetshire, contain very little animal matter, but much 
phosphate of lime ; those in the Kirkdale cave contain 
almost all their phosphate of lime, but have lost a con- 
siderable portion of animal matter: whilst the bones 
dug up at Trasimend or Herculaneum differ very little 
from recent bones. 

These remains of viviparous quadrupeds, found in 
the diluvian strata, most curious in their nature, appear 
to have belonged to animals which no longer exist. 
Cuvier^ to whose genius we owe all the great elucida- 
tions of this mysterious subject, has found that amongst 
upwards of seventy varieties of animals, discovered in 
these strata, eleven only bear a perfect resemblance to 
species now existing, and by &r the greater number 
belong to unknown species, and more than thirty to 
new genera ; and it is remarkable that the species re- 



38 AWARD OF THS COPLEY MEDAL 

aembling those which now inhabit only warm cUmates, 
are found in the toml state in cold ones ; the bones^ 
and even the entire body and skin, of the elephant and 
rhinoceros, in Siberia; and the bones of el^^hants, hip- 
popotami, hyasnas, and animals of the tiger kind, in 
these islands and over the continent of Europe. 

It has generally been admitted by sound reasoners, 
that the manner in which these bones are found buried 
amongst gravel, sand, and water-worn stones, proves the 
operation of a great diluvium — an inundation of the 
waters of the ocean over the land* But, till Professor 
Buckland's paper, there had been no decisive evidence, 
though there had been reasonable conjectures, that 
these animals once existed in the countries in which 
their remains are now found, and that they had not 
been transported by the violence of the inundation or 
of currents acting under very peculiar circumstances, 
from other climates, such as those now inhabited by the 
same species of animals. 

As far as YorkflbU^ and England are concerned, and 
analogy would induce us to conclude, the whole of 
Europe and the northern continent, Professor Buck^ 
land has shown, by fiur inductive reasoning, that a large 
species of hyaena, the rhinoceros, the hippopotamus, 
the elefdiant, and animals <^ the bear and tiger kind, 
once inhabited this country ; and he infers, with some 
degree of probability, that they were destroyed by the 
deluge. Since Professor Buckland's paper has been 
published, I have had the pleasure of visiting the cave, 
in his fioeiety, aod entertun no dmht of the general 
accuracy of his oonelusions. The horizontal nature of 
the fissure^ — ^the immense quantity of bones and teeth 
found in it, — the manner in which they are worn on 
one side, — the marks made by the gnawing of teeth in 



TO THE RBV. DR. BUCKLAND. 39 

many of them, •— the excrements of the animal, — all 
prove the circmnstaoce of the cave having been in- 
habited by hyasnas, probably, by many generations; 
who brought in finom the neighboarhood, such animals 
as they could destroy, or such as, found dead, they 
could tear into pieces. 

You will, I am sure, consider it as a fortunate cir* 
cumstance, that such a phenomenon occurred to so 
accurate an observer as Professor Buckland. The 
nature of the cavern rendered it inaccessible, except in 
quarrying the rock ; fortunately it was closed by sta- 
lactite, and the bones were covered with mud, which 
prevented the action of the included atmosphere upon 
tbem, and, consequently, their decomposition : and thus 
they remained, almost in their primitive state and 
positions, sealed up, — a feithful record, as it were, of a 
past age of the world. 

Since your last Session, Professor Buckland has ex« 
amined various caves in different parts of Germany, 
containing bones ; and the cavity in the limestone^ock 
at Orestou, near Plymouth; of which an account had 
been formerly published in your TransactionSy and has 
confirmed his general conclusions, o<moeming the pe- 
riod at which the animals, to whom the bones belonged, 
lived, and their destruction by a great inundation of 
water. But I shall not anticipate his views, as I hope 
he will himsdf lay them before the Society. 

The existence of animals, of genera now only found 
in warm climates, being estaUished, it becomes a 
curious inquiry whether our tempeimtuie has been 
changed, or whether the di£ferenee in the species, and 
consequently the habits, was such as to enable tfa^n to 
live in temperate or coM diiaates. Professor Buckland, 
with his characteristic caution, has not decided on this 



40 AWARD OF THE COPLEY MEDAL 

question. The ancient hyaena, elephant, and hippopo- 
tamus of this country were, perhaps, as different from 
those of Africa, as the musk ox is fix>m the common ox ; 
yet, supposing the antediluvian climate of Siberia, such 
as it is now, it is difficult to imagine that an animal of 
the elephant species could have found sufficient food 
there, or that a hippopotamus could have inhabited its 
frozen rivers. 

It seems much more likely that the temperature of 
the globe has been changed ; and perhaps suddenly, by 
a great irruption of water fit)m a deep ocean over the 
land. An ancient high temperature of the globe, is 
likewise not only consistent with this view of the sub- 
ject, but likewise with the late observations made on 
the heat of the interior, and with the facility afforded 
by it of explaining many existing phenomena, and 
many mineral productions. I shall not, however, in- 
dulge in any speculations on this subject, which no 
person is more capable of illustrating, than the worthy 
Professor himself 

1 cannot conclude this part of my subject, without 
congratulating the Socie^ that by these inquiries, a dis- 
tinct epoch has, as it were, been established in the his- 
tory of the revolutions of our globe : a point fixed, fix>m 
which our researches may be pursued through the im- 
mensity of ages, and the records of animated nature, as 
it were, carried back to the time of the creation. 

It is gratifying to feel that the prepress of science 
establishes, beyond all doubt, the great catastrophe de- 
scribed in the sacred history, and tibe account of which 
is blended with the traditions of so many ancient 
nations ; and that it likewise demonstrates the circum- 
stance of a primitive chaotic state of the globe, in which 
there was no life, of a successive creation of living 



TO THB REV. DR. BUCKLAND. 41 

beings, of which man was the last, destined to people 
the earthy when its sur&ce had assumed a state of order 
and beauty fitted for the improvement and activity of 
an intellectual and progressive being. 

In comparing such deductions of geology with some 
brilliant speculations of the last century, it is impossible 
not to smile at the aberrations of human genius, and to 
be proud of the progress we have made. 

The eternal order of one simple system, in which the 
same beings, slightly changed, existed, and in which 
water is the destroying, and fire the renovating prin- 
ciple, though supported by so much talent, fisM^t, and 
experiment, has disappeared, for the sound geologist, 
with the more visionary ideas of the earth's being ori- 
ginally a portion of the sun ; and of organized germs 
passing, in the immensity of time, through the different 
stages of improvement, rising firom fishes through mer- 
maids, quadrupeds, and apes: and, at last, perfect in 
man! 

Hypotheses and dreams of this kind are now rejected ; 
and so ought to be all those views, in which systems of 
geology are attempted to be firamed out of the sacred 
writings, by wresting the meaning of words, and altering 
the senses of things. Lord Bacon long ago raised his 
voice against this mode of proceeding : grand facts in 
the history of the globe are given, but not systems of 
philosophy* Man has no right to measure divine truths 
by his own fancies or opinions : they should be kept 
perfectly distinct. The more we study nature, the more 
we obtain proo& of divine power and beneficence ; but 
the laws of nature and the principles of science were to 
be discovered by labour and industry, and have not 
been revealed to man ; who, with respect to philosophy, 
has been left to exert these god-like faculties, by which 



42 AWARD OF THE COPLEY MEDAL 

reason ultimately approaches^ in its results^ to inspira* 
tion. 

Mb. Bdckland, 

Receive this medal) as a proof of the high estima- 
tion in which your labours and researches are held by a 
body which) I believe, is very impartial in its decisions^ 
and which) I trust, looks to the actual progress science 
has made, rather than the person, school, or nation, to 
whom it has been owing. I know I need not ui^e you 
to a further pursuit of these inquiries, by which you 
have gained distinction, and so much merited popularity. 
You are, I am sure, devoted to them^ and I only wish 
you health to enable you to pursue them ; for I am coa* 
vinced that the longer you Uve, the more extended wUl 
be the obligations you will confer on the world of 
science; I hope your example will stimulate some of 
the younger Fellows of the Society to similar researches. 
It is, as it was originally, the Royal Society for the im^ 
provement of natural knowledge; and we have been, and 
always are, most happy to receive important &cts^ laws, 
and principles respecting the mineral history of the 
eartL We deeply feel die use and the importance of 
such inquiries, in their relations to the prepress of the 
arts, as well as to the sublimer speculations of philo- 
sophy. How intimately, for instance, is agriculture, on 
which nations depend for their powers of supporting 
and multiplying a happy population, connected in its 
progress with the knowledge of the nature of soils, of 
the sub«strata and strata of the earth, and of fossil ma* 
nuresi How much is architecture, next perhaps in 
utility, dependent for its resources upon an acquaint- 
ance with the nature and situation of stony substances, 
necessary for permanent structures, and those qualities 



TO THE REV. DR. BUCKLAND. 43 

of them which occasion their decomposition, or their 
permanency I And how great a part of the actual 
strength^ as well as the wealth of countries, depends 
upon their metalhc and mineral veins and strata — upon 
their coal and their iron, which, applied by chemical 
and mechanical ingenuity, have, as it were, caused the 
elements to labour for man I 

Nor is this study, as no one has better explained than 
yourself^ without its moral benefits, affording happy 
views, where they might least be expected, of the eco- 
nomy of nature : the great mountain-chains equalizing 
the temperature of the globe, and, by their elevation, 
rendering warm climates habitable ; the ocean being a 
reservoir of heat, and the rocky strata serving not 
merely as the support of soils, but causing a distribution 
of the water poured down from the atmosphere, for the 
purposes of vegetable and animal life. Then, in the 
history of the past changes of the globe, what a sublime 
subject is there for the exercise of the imagination ! 

If we look with wonder upon the great remains of 
human works, such as the columns of Palmyra, broken 
in the midst of the desert, the temples of Paestum, beau- 
tiful in the decay of twenty centuries, or the mutilated 
fragments of Greek sculpture, in the Acropolis of 
Athens, or in our own Museum, as proofs of the genius 
of artists, and power and riches of nations now passed 
away ; with how much deeper a feeling of admiration 
must we consider those grand monuments of nature, 
which mark the revolutions of the globe : continents 
broken into islands ; one land produced, another de- 
stroyed ; the bottom of the ocean become a fertile soil ; 
whole races of animals extinct, and the bones and ex- 
uviae of one class covered with the remains of another ; 
and upon these graves of past generations, the marble 



44 AWARD OF THE COPLEY MEDAL. 

or rocky tombs, as it were, of a former animated world, 
new generations rising, and order and harmony estab- 
lished, and a system of life and beauty produced, as it 
were, out of chaos and death; proving the infinite 
power, wisdom, and goodness of the Great Cause of all 
being! 



45 



DISCOURSE OF THE PRESIDENT, 
Anhiybsbabt, Dec. Ibt, 1828, 
On theChaneten of Dr. Hutton, Dr. Jbnnbb, Dr. Baillib, Colonel 
Lambtok, Archdeacon Wollaston, Dr. Cabtwbioht, and Mr. 
Joboan; and on the Award of the Copley Medal to John Pono, 
Eflq., Astronomer Royal, for his various Papers on Subjects of Astro- 
nomy, published in the Philosophical Transactions. — ^With General 
Views of the Present State of Astronomy, and on the Accessions made 
to this Branch of Science, in the Royal Observatory at Greenwich. 

After perusing this list of deaths I cannot avoid say- 
ing a few words on the characters of some of the 
Fellows whom we have had the misfortune to lose. Of 
course I can only speak of such as, by their communis 
cations to the Society or philosophical labours, have 
promoted the progress of science* Those who have 
other claims to public consideration will receive their 
applause in other places. Here a tribute of respect to 
the memory of the dead, who have promoted the ob- 
jects of the Society, is called forth by gratitude, and it 
may perhaps awaken a feeling of emulation in the 
living. 

The labours of more than half a century. Gentlemen, 
have established the reputation of Dr. Hutton, as one 
of the most able mathematicians of his country and his 
age. 

His papers, published in the Transactions of the 
Royal Society on Conveiging and Infinite Series and 
Cubic Equations, and his elementary and original works 



46 CHARACTERS OF SOME DECEASED FELLOWS. 

on various branches of the science of quantity, prove the 
extent of his knowledge, his industry, and his penetra- 
tion. And, during the long period that he was Pro- 
fessor at Woolwich, he may be regarded as having emi- 
nently contributed to awaken and keep alive that spirit 
of improvement among the military students which has 
so much exalted the character of the British officer, and 
which has been attended with such beneficial results to 
the country. Dr. Button's merits, as an experimental 
philosopher, were of no mean kind, and they are dis- 
played in his paper on Gunnery, for which he was re- 
warded with the Copley Medal, by the President and 
Council of the Roysd Society, in 1778. In this paper 
he extends the views and inquiries of Robins by many 
difficult and delicate experiments on the force of gun- 
powder, and draws conclusions which have been con- 
nected with important practical results. But perhaps 
Dr. Hutton's greatest work was his calculation of the 
density of the earth, founded upon Dr. Maskelyne's ex- 
periments of the effect of the attraction of Schehallien 
on the plumb-line, in which a simple quantity was to be 
discovered by the most complicated arithmetical pro- 
cesses, and which required great devotion of time and 
labour. His name, on this occasicm, will ever be asso- 
ciated with one of the grandest and most important 
physical problems solved in the last century, and wriU 
pass down with honour to posterity. 

Dr. HuttoB, as you well know, died at a very ad- 
vanced age, and retained the vigour of his faculties. 
Nothing, indeed, can be a strongerproof of this than his 
paper communicated to the Royal Society in 1821, 
when he was eighty-four years of age, and which <jon- 
tains a comparison of Dr. Maskelyne's and Mr. CaveD- 
dish's experiments on the density of the earth, and a 



CHARACTERS OP SOME DECEASED FELLOWS. 47 

number of corrections of very <fifficiik and intricate cal- 
culations. 

To speak of Dr. Edward Jenner as a man of science 
of our own particular school^ would be saying little; he 
has a higher claim to oar deep regret and profound ad- 
miration, as a bene&ctor to mankind in general. 

It is needless for me. Gentlemen, to dwell upon the 
effects of vaccinaticm, but I may say something of the 
nature of the discovery. It often happens, that when, 
by enterprise, ingenuity and unwearied application to 
one tram of thought or experiment,, some great £$ep is 
made in practical or theoretical science, persons of com* 
mon minds, in considering the simplicity of the result, 
are apt to undervalue the labour by which it was at- 
tained, and to refer to accident what has been really 
effected by the highest operaticms of tike human under- 
standing. That persons who had passed through a cer- 
tain disease, communicated by cattle, were not liable to 
variolous infection, had perhaps been known amongst 
the vulgar for more than a century ; but without tibe 
investigation of Jenner, this knowledge would have re- 
mained hidden from the scientific world, and perhaps 
been regarded as a vulgar prejudice. Lord Bacon has 
said, '^ there are short methods for men of genius ;" but 
it might, perhaps, with more propriety be said, there are 
yiew methods for men of genius. Their characteristic 
is, that they do not walk in beaten roads, and that in 
seeing an object before them, they are neither deterred 
by danger or the fear of ridicule, firom following it 
through unfrequented paths. The originality of Dr. 
Jenner's mind and his accuracy ot observation, are 
shown in his first communication to the Royal Society, 
on the natural History of the Cuckoo; and, in pursuit 



48 CHARACTEBS OF SOME DECEASED FELIX)W8. 

of hb great object, he met with obstacles which it re- 
quired no ordinary degree of perseverance and of con- 
fidence in his own powers to overcome. 

The figdr way of judging of the merits of an inventor, 
is by the operation of his discovery in civilized and so- 
cial life : and, in this respect, Dr. Jenner stands almost 
alone, having subdued a positive evil, having secured a 
benefit not only for all the present inhabitants of the 
earth, but for their most remote posterity : gaining for 
his name the most enviable kind of immortality, that 
connected with the gratitude and blessing of his fellow- 
creatures, and which will be more valued in proportion 
as men estimate more correctly the nature of true glory. 

It is difficult, in speaking of those with whom we have 
been connected by ties of firiendship, whom we have 
admired and reverenced, to be strictly impartial ; yet I 
believe that the merits of Dr. Matthew Baillie can 
hardly be estimated too highly, even by those who had 
the warmest feelings of affection for his memory. Whe- 
ther considered as a physician or as a man, his talents 
and his virtues were alike distinguished. His works 
show the accuracy and coolness of his judgment, his 
minuteness of observation, and his acuteness in referring 
effects to their true causes, amidst the complicated phe- 
nomena offered by diseased organs. Whoever heard 
him give his opinion in the Council of the Royal So- 
ciety, was struck by the clearness and simplicity of his 
details, and the happy manner in which he caught the 
relations and explained the nature of a scientific subject 
in which he was interested. 

Those who have seen him by the bed-side of the 
sick, who witnessed the kindness of his nature, the 
deep interest that he took in the sufferings and danger 



CHARACTERS OF DECEASED FELLOWS. 49 

of his patients, will, above all, estimate the nobleness 
and disinterestedness of his conduct. An honour to 
his profession in public life, he was most amiable and 
exemplary in his intimate social relations and domestic 
habits. No man was ever freer from any taint of 
vanity or affectation. He encouraged and admired 
every kind of talent, and rejoiced in the success of his 
contemporaries. He maintained, even at court, the 
simplicity and dignity of his character. His greatest 
ambition was to be considered as an enlightened and 
honourable physician. His greatest pleasure appeared 
to be in promoting the happiness and welfare of 
others.* 

With respect to Colonel William Lambton, a veteran 
in the army of India, and who was personally known 
to very few Fellows of the Society, I can speak only 
of his works, and refer you to the two papers published 
in the Transactions^ on the Admeasurement of an Arc 
of the Meridian in Hindostan, a work of great labour, 
displaying minute accuracy and extraordinary perse* 
verance, and carried on in a climate unfavourable to 
bodily exertion or intellectual pursuit. This arc ex- 
tends in amplitude nearly 10°, upwards of 9° 53', from 

* [There never was a man^ I believe, more respected by his profes- 
sional brethren ; a strong proof of moral excellence, as well as of high 
attainments. The last time I ever saw Dr. Baillie, proof was given of 
this feeling ; it was, when in a valetudinary state, not many months 
before his death ; it was at a large meeting of medical men, amongst 
whom were some of the most distinguished of the metropolis. Owing to 
his infirm health Dr. Baillie rose firom table early in the evening ; there 
was a spontaneous rising of the whole company, and before he could 
quit the room his health was drank with acclamations, and in such a 
manner as to affect him sensibly, as was very apparent from the tremu- 
lous tones of his voice in his reply to the compliment. Never before 
or since have I witnessed such a demonstration of professional respect] 

VOL, VII. D 



50 CHARACTERS OF DECEASED FELLOWS. 

Cape Comorin to Namthabad ; and Colonel Lambton 
has the honour of having laid down the largest con- 
nected portion of the meridian ever measured upon the 
surface of the globe ; a work not only of importance in 
its relation to the figure of the earth, but constituting 
the foundation for a correct survey of our extensive 
possessions in India. 

Of Archdeacon Wollaston, whose recent and sudden 
death has occasioned so much affliction to his &mily 
and friends, I can only say, that the little he communi* 
cated to the Royal Society makes us feel regret that he 
was not a more frequent contributor to our Tramajc^ 
tions. His paper on the Measurement of Heights, by 
the Alteration of the boiling Temperature offers a 
valuable resource in ascertaining the altitude of moun- 
tains, and is remarkable for accuracy of method and 
distinctness of detail. I have always understood, 
that as a Professor in the University of Cambridge, 
his lectures were admirable ; and he was worthy of 
a family in which talents and virtues seem to be 
hereditary. 

Dr. Cartwright became a Fellow of the Society late 
in life. He was a very amiable man, possessed of 
literary talents, much mechanical ingenuity, and great 
enthusiasm in the exercise of it : and he received a 
parliamentaiy reward for a mechanical invention which, 
I believe, has been of considerable use to the manufac- 
tures of the country. 

Mr. Jordan was attached to science, and pursued 
with ardoiu: a branch of optics, on which he published 
a work ; he had the merit of attending to philosophical 



AWARD OF THE COPLEY MEDAL. 51 

subjects amidst the duties of a profession which is rarely 
associated with scientific habits. No communications 
either of Dr. Cartwright or Mr. Jordan have been pub- 
lished in your Transactions, 

COPLEY MEDAL. 

From the melancholy office of speaking of the merits 
of your deceased Fellows, I now pass to the more 
pleasing duty of stating the useful labours and active 
exertions of a living philosopher. 

Your Council, Gentlemen, have awarded the medal 
of Sir Godfrey Copley's donation, for the year 1823, 
to John Pond, Esquire, Astronomer Royal, for his 
various papers and observations communicated to the 
Royal Society. 

The merits of Mr. Pond, as an inde&tigable scien- 
tific observer, are fully and justly estimated by all the 
Fellows of this Society, who have visited or taken any 
interest in the Royal Observatory; but, perhaps, the 
early devotion of the Astronomer Royal to his favourite 
science, the enthusiasm with which he pursued it, and 
the sacrifices of time, health, and money that he made 
in consequence, may be less generally known. 

Twenty-five years ago, Mr. Pond, animated by his 
love of astronomy, carried, at a considerable expense, 
some valuable instruments to the coasts of the Mediter- 
ranean, hoping that a purer atmosphere and a brighter 
sky would give him advantages for pursuing continued 
observations on the fixed stars, not to be obtained in 
the variable climate of this island, and he passed some 
time devoted to his scientific objects at Lisbon, Malta, 
and Alexandria; but the state of his health obliged 
him to return, and he established himself at Westbury, 

B 2 



52 AWARD OF THE COPLEY MEDAL 

in Somersetshire, where, in 1800, I had the pleasure of 
visiting him, and when I was delighted to witness the 
ardour with which he pursued his inquiries ; and saw 
with admiration, the delicacy of his observations with 
the astronomical circle of Mr. Troughton's construc- 
tion. 

The researches made at Westbury, by Mr. Pond, on 
the declinations of some of the fixed stars, in 1800, and 
])ublished in the Philosophical Transactions for 1806, 
fixed the attention of astronomers by their accuracy and 
the clearness of the details ; and probably principally 
caused those scientific recommendations which inclined 
our august Royal Patron, then Prince Regent, to ap- 
]>oint him to the distinguished office which he now 
holds. 

Since Mr. Pond has been Astronomer Royal, his 
communications to the Royal Society have been nume- 
rous, and many of them of great importance. 

I shall mention some of the most considerable : — 

In 1813, A Catalogue of the North Polar distances 
of thirty -four of the principal Fixed Stars, deduced from 
Observations made with the Mural Circle, at the Royal 
Ol^servatory. 

In 1815, Determination of the North Polar Distances, 
and proper Motions of thirty Fixed Stars. 

In 1817, Three Papers on the Parallax of the Fixed 
Stars. 

In 1818, On the different method of constructing a 
Catalogue of the Fixed Stars : on the Parallax of a 
Aquilse, and on the Parallax of the Fixed Stars in right 
Ascension. 

In 1823, Three Papers on the Changes that have 
taken Place in the Positions of some of the Fixed Stars, 
and a Paper on the Parallax of a LyrsB. 



TO MR. POND. 53 

It is very difficult, or almost impossible to point out 
the specific merits of astronomical observations* They 
are not like philosophical or chemical experiments, 
which produce an immediate result ; their delicacy and 
exactness can only be judged of by persons who have 
seen the manner in which they are made, and who are 
accustomed to the same kind of labour. They often 
relate to long periods of time, and their correctness and 
value can only, perhaps, be fairly estimated by pos- 
terity. 

The two principal points of discussion in these papers 
of the Astronomer Royal, are, the grand and long-agi« 
tated question of the parallax of the fixed stars, and an 
apparent decUnation or change of position in a number 
of the stars, not to be accounted for by any known laws. 

Since the Copernican system was first received as the 
true system of the universe, by the enlightened philo- 
sophers of Europe, the inquiry, whether the fixed stars 
had any annual parallax, has been constantly brought 
forward. 

It was evident that the diameter of the earth would 
not afford any difference of angle with bodies so im- 
mensely distant as the stars, but it was hoped, that 
such a difference would be observed at the two extre- 
mities of its annual orbit, distant firom each other nearly 
one hundred and ninety millions of miles. 

Flamstead supposed he had observed a considerable 
annual parallax ; but the observations of Bradley proved 
that the phenomena which he described were owing to 
another cause, and he solved them by his grand dis- 
covery of the aberration of light. The subsequent ob- 
servations of Bradley, with the great sector constructed 
by Graham, the instrument that he had likewise used 
in his former researches, led to no result favourable to 



54 AWARD OF THB COPLEY MEDAL 

parallax ; and the minute and accurate observations of 
the late Astronomer Royal were on the same side of 
the question. 

Between 1800 and 1806^ Piazzi imagmed that he had 
proved a parallax of some seconds, and Dr. Brinkley, in 
1810, communicated through Dr. Maskelyne, his obser- 
vations on a LjrsB, made with the great eight-feet 
Dublin circle, and which, he conceived, showed that the 
parallax of that star could not be less than 2" or 2^'\ 
This star, and other stars, have been observed with great 
accuracy, by Mr. Pond ; and his conclusions, both from 
the use of a fixed instrument, and of the great circle, 
are, that none of the fixed stars, which have come under 
his observation, have any sensible parallax, and that the 
parallax of a Lyrae, if it exist at all, cannot exceed a 
very small fi:tM;tion of a second ; his general conclusions 
are thus stated by himself: ^ The observations of this 
year have produced on my mind a conviction approach- 
ing to moral certainty. The history of annual parallax 
seems to be this — ^in proportion as instruments have 
been imperfect in their construction, they have led ob- 
servers into the belief of sensible parallax : this has hap- 
pened in Italy to astronomers of the very first reputa^ 
tion. The Dublin instrument is superior to any of a 
similar description on the Continent, and, accordingly, 
it shows a much less parallax than the Italian astrono* 
mers imagined they had detected. 

^^ Conceiving that I have established, beyond a doubt, 
that the Greenwich instrument approaches still nearer 
to perfection, I can come to no other conclusion, than 
that this is the reason why it discovers no parallax at all.^ 

Dr. Brinkley has not yet replied to Mr. Pond's latest 
examination of this subject ; but in an elaborate paper, 
published in the Transactions for 1821, he enters into a 



TO Ma POND. 55 

full discussion of the question^ and displays^ as usual, 
the most profound views of the causes which may affect 
his observations, and the greatest acuteness in examin- 
ing the objections that have been made to his conclu- 
sions, and he endeavours to confirm them by new obser- 
vations, and is still of opinion, that many of the fixed 
stars have a sensible parallax. In awarding the medal 
to Mr. Pond, the Council of the Royal Society do not 
at ail mean to express an opinion on this subject : when 
two such astronomers differ, it would be presumptuous, 
and almost impossible, for them to decide ; it is, how- 
ever, highly satisfiustory to know that the question is 
now reduced within such very small limits, the differ- 
ence between the Greenwich and the Dublin observa- 
tions generally amounting to less than a second. Those 
who read Dr. Brinkley's and Mr. Pond's papers with 
attention, can alone judge of the refinements of modem 
observation, and of the perfection to which the genius 
and labour of Mr. Troughton have carried our instru- 
ments, and of the extreme difficulty and delicacy of this 
investigation, in which the smallest differences of tem- 
perature, and (when stars are not in the zenith) of the 
refiractive power of the atmo8]>here, produce immense 
results, and where perfect stability of the instrument of 
the building, and of the ground on which it stands, are 
absolutely essentiaL 

With respect to the second great point in Mr. Pond's 
papers, the apparent variation in the position of many 
of the fixed stars ; the novelty of the subject and the 
great importance of its relations, and the very short 
time that has elapsed since it has been brought before 
the Society, and the necessity for its confirmation by 
the observations of a long series of years, so as to dis- 
cover the true cause, render it impossible for me to do 



56 AWARD OF THE COPLEY MEDAL 

more than state the supposed result^ and the manner in 
which it was obtained. 

Yon will well remember the candour with which the 
Astronomer Rojal communicated to the Society the 
account of an accident which had happened to the 
mural circle. In examining the supposed errors in 
the places of fixed stars owing to this accident, he 
at first rated them high ; but after the instrument was 
put in a state of perfect repair, he found, by the most 
delicate observations, that a part of what he considered 
an error, appeared to be really owing to a southern 
declination of many of the principal fixed stars, and 
that their real places were considerably further south 
than their predicted places, as discovered by ancient 
catalogues. After considering the subject under eveiy 
point of view for more than twelve months, and 
examining the most correct catalogues, the Astronomer 
Royal is still of the same opinion on this subject, and 
he considers this apparent change in the position of the 
principal fixed stars, as incapable of being accounted 
for from any source of error in the instrument or mode 
of observation, and as pointing out to some unknown 
and new principle. However improbable this may at 
first view appear, it will be recollected by the Fellows 
of this Society, that the first germs of the great dis- 
coveries of Bradley, — the Aberration of Light, and the 
Nutation of the Axis of the Earth, — were observations 
of this kind, but nearly a quarter of a century was re- 
quired for the full development of these grand truths. 

Should the southern declination be ultimately es- 
tablished, a motion towards, or slow revolution of the 
sun round some part of the sidereal world, seems a 
much more probable cause of explanation than any new 
unexplained relations of the system to light, or any un- 



TO MR. POND. 57 

known motion of the axis of the earthy or any proper 
motion, in one direction, of the great body of the stars. 
Bat these are points for future discussion, upon which 
no man is more able to enter than the Astronomer 
Royal himself; let us hope that he will verify, and 
place beyond doubt, this important but still uncertain 
result, and that it will lead to a new law in nature, and 
add another important discovery to those which we 
already owe to the labours carried on in the Royal 
Observatory, and which have so much contributed to 
the progress of astronomy, and to the glory of our 
country. 

I cannot touch upon this subject without saying a 
few words more, for it is one which ought to call 
forth feelings of gratitude and admiration in every 
Fellow of this Society. 

How distinctly the results obtained there prove the 
utility, almost necessity, of the foundation and the 
patronage of some such establishments by government ; 
for since the existence of this noble Institution, what 
lasting benefits has it conferred on science and the 
public! 

I remember the late excellent Secretary* of the 
Royal Academy of Sciences at Paris, said to me, in 
conversation ten years ago, " Such is the excellence and 
extent of the Greenwich observations, that if all the 
other records of science were destroyed, they alone 
would be sufficient to found a system of astronomy." 

In going back to Flamstead's time, we find them 
taken by all Europe as the models to be followed in 
similar estaljlishments. Of Ualley, a philosopher of a 
higher stamp, and inferior, perhaps, only to his friend 
and master, Newton, it is scarcely possible to speak 

* [M. Delambre.] 

d5 



5S AWARD OF THB COPLEY MEDAL 

with sufficient praise. The observations of the transits 
of Venus, the determination of the solar parallax, the 
investigation of the Newtonian law of cometary motions, 
and the prediction of the return of the comet of 1682^ 
in 17599 the foundation of the method for observing the 
lunar motions, and the accurate observations of that 
satellite for more than nine years, — ^labours which have 
led to the construction and perfection of those tables 
which are of such immense importance to navigation, 
and which may be said to have given us the discovery 
of the longitude at sea, — are a few amongst the obliga- 
tions of astronomy to this great man. 

Of Bradley, it may with truth be said, that he was 
worthy to succeed Halley, and his name is immortalized 
by the two most important discoveries ever made with 
respect to the system of the heavenly bodies. 

Of Dr. Maskelyne, whom we remember with so 
much respect and affection, it is only necessary to say, 
that his was a kindred spirit to that of those illustrious 
philosophers; and whether determining the density 
of the earth in his shed on Schehallien, or observing 
the fixed stars with unwearied attention at Greenwich, 
he was always the same padent, acute, sagacious, and 
unprejudiced observer. 

Without an establishment provided by the liberality 
of government, without that retirement and philosophic 
leisure afforded by their situation, without instruments 
requiring an expense which few individuals can com- 
mand, these distinguished men might almost have 
been bom in vain ; and what a recompense has been 
bestowed on the nation, for the few hundreds of pounds 
annually devoted to this object I The greatness of this 
country has arisen with its maritime and colonial em- 
pire ; and how much has the Royal Observatory done 



TO MR. POND. 59 

for the perfection of navigation^ and the interests of our 
navy ! A misfortune like that, by which one of our 
noblest fleets and bravest admirals were lost on the rocks 
of Scilly, not much more than a century ago, can now 
never happen again ; and, independent of the common 
question of utility, what an immense effect has the pro- 
gress of astronomy, following and confirming those 
views of the system of the universe of our own illus- 
trious Newton, had upon the improvement of general 
science, thus enlightening and exalting the human in- 
tellect I All thastiperstitious notions, all the prejudices 
respecting the heavenly bodies, which had such an effect 
upon the destinies of individuals, and of kingdoms in 
ancient times, have disappeared. Man, acquainted 
with his real situation in the scale of the universe, has 
learned to appreciate his objects, and the ends of his 
creation. A mere drop in the ocean of infinity, he has 
yet sufficiently felt his divine and intellectual nature, to 
elevate his mind firom the minute base of the earth to 
the heavens, to investigate the laws of bodies invisible 
to him, except by instruments of his own invention, and 
hundreds of millions of miles removed from him. And, 
in the progress of his knowledge, he has seen obscurity 
vanish, motions which, considered for a short space of 
time appeared disorderly, he has found belonging to an 
extensive and regular cycle; and in what seemed 
sources of confusion and imperfect machinery in the 
constitution of things, as new lights have poured in 
upon him, he has found causes of order and harmony. 
So that modem astronomy, as it now exists, is the 
noblest monument ever raised by man to the glory of 
his Maker: for its ultimate and refined developments 
demonstrate combinations which could only be the re- 
sult of infinite wisdom, intelligence, and power. 



60 AWARD OF THE COPLEY MEDAL TO MR. POND. 

Mb. Astronomer Royal, 

I now present to you this medal, as a token of the 
respect of the Society, and of the confidence of the 
Council, in the great accuracy of your observations, and 
likewise as a memorial that fbture important labours in 
the same department of science are hoped for, nay ex* 
pected, firom you. 

I am well aware, that some of the greatest and most 
important objects of discovery, and those perhi^s most 
obvious, have been obtained by the labours of your pre- 
decessors, and that in proportion as the field is Investi- 
gated, new results become rare, as well as more difficult 
to be discovered ; yet nature is inexhaustible, and the 
powers and resources of the human mind, and the re- 
finements of art, have not as yet attained their limits. 
Who would have anticipated, half a century ago, the 
discoveries of Ilerschel and Piazzi ? — Though pursuing 
a science that may be considered as in its maturity, you 
have advantages of a peculiar kind, more perfect instru* 
ments than were ever yet employed, more extensive 
assistance than any of your predecessors; and upon 
these points, the liberality and promptitude with which 
Government have entered into your views, and those of 
the Council of the Royal Society, for the improvement 
of the Royal Observatoiy, cannot be too much admired. 
Continue to pursue your honourable career, and endea- 
vour to be worthy of having your name transmitted to 
future generations with those of your illustrious prede- 
cessors. 

Of all the branches of science, astronomy is that fix>m 
which this Society has gained most glory ; and it never 
has lost, and I am convinced never will lose, any oppor- 
tunity of advancing its progress, and honouring its suc- 
cessful and zealous cultivators. 



61 



DISCOUBSB OP THE PRESIDENT, 

An NITERS ART, 1824. 

Chuacter of Baron Maserbs. — Award of the Coplbt Medal to the 
Ber. Dr. Brinki.bt, now Bishop of Cloyne, for his Mathematical 
and Astronomical Papers published in the Philosophical Transac- 
tions. — ^With Views on some Refined Questions of Astronomy, and on 
the General Importance and Sublime Views of this Science. 

Ik reading over this list, though there is one person of 
extraordinary genius/ still an object of deep interest in 
the literary worlds and though other names occur con- 
nected with useful professional labours, yet the only 
character which I am called upon to notice, as a contri- 
butor to your Transactiansy and as an active scientific 
member of the Society, is that of Baron Maseres. He 
may be considered as belonging to the old mathematical 
school of Britain; and through a long life devoted much 
of his leisure and a portion of his fortune, to the pur- 
suit and encouragement of the higher departments of 
algebra and geometry. Four of his papers are pub- 
lished in your Transactions, — two on Infinite Series, 
and two on the Extension and Discovery of Cardan's 
Role. He printed, at his own expense, the Smptores 
LogarUhmicif and an extensive and laborious work on 
Negative QuanHHeSy in which he took a very peculiar 
view of this abstruse subject. He was fonder of inves- 
tigating the principles of the mathematical sciences, 
than of attempting applications of them. His love of 

* Lord Byron. 



62 AWARD OF THB COPLEY MBDAL 

science was of the most disinterested kind, as is shown 
by the nature of his publications, and by the liberal 
way in which he encouraged the publications of others. 
He died in extreme old age, having almost outlived his 
faculties. 



COPLEY MEDAL. 

In following the course of the business of the day, I 
have to announce to you the decision of your Council 
with respect to the medal of Sir Godfrey Copley's 
donation to the Society. 

It has been awarded this year to the Reverend John 
Brinkley, D.D. Andrew's Professor of Astronomy in 
the University of Dublin, and President Br.LA*, for his 
various communications printed in the PhilosapMcal 
Tranaojctions, 

To some of the members of the Society, who have 
not followed closely the usages of the Council, a ques- 
tion might at first sight arise upon the decision, why 
in two successive years the cultivators of a science, 
which, during that time, has been distinguished by no 
remarkable discoveries, should receive the highest 
honours which this Philosophical Association has to 
confer. 

A very short explanation will, I trust, suffice. The 
progress of science has no annual periods; and when a 
medal is to be bestowed every year, not merely impor- 
tant scientific £su;ts, but likewise trains of useful labours 
and researches must be considered ; and the zeal, ac- 
tivity, and knowledge of those persons, who, having 
been contributors to your Transactions, must be re- 
garded as competitors, are to be taken into the account 

It has now and then happened that ihe Royal Society 



TO DR. BRINKLEY. 63 

has had the felicity to mark some great and brilliant 
discoveiy^ such as tliat of the aberration of light, or the 
magnetic effects of electricity, by this token of its 
respect ; but in general, of necessity, the medal is be- 
stowed for contributions of a more humble character. 
To reward those laborious philosophers who enlighten 
science by correct observations or experiments, or those 
sagacious inquirers who by accurate reasonings or in- 
genious views, lay the foundation for new researches, 
new theoretical arrangements, or applications of science 
to the uses of life ; and if any one department of 
natural knowledge requires encouragement more than 
another, it is astronomy ; for having arrived at a mature 
state, and presenting few striking objects of discovery, 
it can only be perfected by the most minute, laborious, 
and delicate inquiries, which demand great attention, 
great devotion of time, and which must often be carried 
on at a period usually destined to repose, and often 
with the sacrifice of health. 

Whoever considers these circumstances will, I am 
convinced, be satisfied of the justice of this vote of 
your Council 

Dr. Brinkley has long been known as an enlightened 
and profound mathematician. His labours, published 
in the Memoirs of the Royal Irish Academy, contain 
abundant proofe of his skill in the higher departments 
of analysis, but it is not necessary to look any where 
else for a demonstration of this, than in our own Trans- 
actions. The volume for 1807 contains an important 
paper, on the General Term of a Series in the Inverse 
Method of finite Differences ; in which, taking up a 
subject of investigation on which both La Grange and 
La Place had written, he has surmounted a difiiculty 
which had remained even after the investigations of 
these illustrious geometers. 



64 AWARD OF THE COPLEY MEDAL 

Whoever is in possession of the higher resources 
of the mathematical sciences, may be considered as 
gifted with a species of power applicable to eyeiy de- 
partment of physical knowledge. It is indeed fi>r 
this species of knowledge, what muscular strength 
is for the different branches of human labour; it not 
only generalizes the results of experiment and observa- 
tion, but likewise corrects them, and leads to new and 
more refined methods of investigation. The guide of 
the mechanical and pneumatical philosopher, and the 
useful assistant of the chemist, it is of still more impor- 
tance to the astronomer, whose results depend entirely 
upon magnitude, time, and motion. 

Endowed in so high a degree with one of the essen- 
tial characters of an accomplished astronomer, his vari- 
ous later communications to the Royal Society, show 
that Dr. Brinkley is equally distinguished as a labori- 
ous, acute, and accurate observer. Your Transactions 
contain seven of his papers, on pure astronomical sub- 
jects: — 

The first. On the Parallax of a Lyrae. 

The second. On the Parallax of certain Fixed Stars. 

The third. The Results of Observations made at the 
Observatory of Trinity College, Dublin, for determin- 
ing the Obliquity of the Ecliptic, and the Maximum of 
the Aberration of Light. 

The fourth. An Account of Observations made with 
the eight' feet Astronomical Circle since the beginning 
of 1818, for investigating the Effects of Parallax and 
Aberration on the Places of certain Fixed Stars ; also 
the Comparison of them with former Observations for 
determining the Effects of Lunar Nutation. 

The fifth. On the Elements of the Comet seen by 
Captain Basil Hall at Valparaiso. 



TO DR. BRINKLEY. 65 

The sixth and seventh, two papers communicated in 
die last year, — the first. On the North Polar Distances 
of the principal Fixed Stars, — the second. Additional 
Observations on the Parallax of a Lyrae. 

On the high merits of these communications, there 
is, I believe, but one opinion amongst competent judges, 
not merely at home, but (I can speak from my own 
immediate knowledge,) likewise abroad. 

Dr. Brinkley has taken up no difficult object of re^ 
search, without first satisfying himself of the correct- 
ness of his instruments by numerous preliminary and 
delicate trials. He has likewise, in forming his conclu- 
sions, examined with philosophical precision all the 
circumstances which may interfere, and he states the 
results with the utmost candour, creating difficulties for 
himself, and proceeding with the greatest caution in 
these fields of inquiry which had been already entered 
in vain by so many illustrious men. 

You well know. Gentlemen, that Dr. Brinkley and 
the Astronomer Royal are at issue on two great and 
leading questions of Astronomy — first, the sensible 
parallax of some of the fixed stars, — and secondly, on 
the apparent southern motion or declination of parts of 
the sidereal system. You know that sensible parallax 
is denied by Mr. Pond, and believed to exist by Dr. 
Brinkley ; that, on the contrary, the southern declina- 
tion is denied by Dr. Brinkley, and believed to exist by 
Mr. Pond* 

I mentioned, in announcing the award of the medal 
last year, that the Council of the Royal Society had no 
intention of giving its sanction to the opinions of the 
Astronomer Royal, or of attempting to decide on these 
important and difficult questions. I again feel it my 
duty to make the same reservation on this occasion, and 



66 AWARD OF THB COPLEY MEDAL 

to State that the general labours of Dr. Bnmkley, on the 
most difficult parts of astronomy^ and the approxima- 
tion to the solution of a great problem, and the high 
merits of his philosophical inquiries, are the sole grounds 
on which the Copleian medal has been bestowed. 

The Council could not with propriety form an 
opinion on these subjectsf, when two such astronomers, 
possessing such peculiar qualities for observation, and 
such varied and exalted resources, are at variance ; and 
the difficulty and delicacy of the questions, will per- 
haps be fiilly perceived by the addition of some short 
details to those given last year on these obscure branches 
of sidereal astronomy. 

When Copernicus first developed that sublime system 
of the planetary worlds which has since been called 
after his name, he was obliged to suppose the fixed stars 
at an almost infinite distance; and the astronomical 
instruments of that day offered no means even of at- 
tempting the discovery of their parallax. The impor- 
tance of such a discovery was, however, immediately 
felt, as a demonstration of it would, in fact, become 
likewise an absolute demonstration of the Copemican 
system of the universe. 

GaUleo seems to have suggested the method of in- 
quiry for parallax, by examining the relative position 
of double stars, at the two extremities of the earth's 
orbit; a method founded on the supposition that the 
stars differ greatly in distance. This method, likewise 
strongly recommended by Dr. Wallis, was first, I be- 
lieve, practised and pursued with great sagacity and 
industry by Sir William Herschel : and though it has 
furnished many important results, with respect to the 
proper motions of their stars, and the arrangement and 
groups of these heavenly bodies, it has as yet afforded 



TO DR. BRINKLEY. 67 

no observations fonning data for reasoning on the dis- 
tance of the fixed stars from the sun. 

The other method, and that which has been most 
insisted upon, seems likewise to have originated with the 
illustrious Florentine philosopher, that of observing 
stars about the summer and winter solstice in or near 
the zenith, for the purpose of avoiding the errors of 
refraction, by fixed instruments. The celebrated Robert 
Hooke, who erected at Chelsea a telescope thirtj-six 
feet long, for examining y Draconis, imagined that he 
had discovered a very considerable parallax for this star, 
but Hooke's observations were contradicted bj those of 
Molyneux. Flamstead drew a similar conclusion from 
his experiments on the pole-star, but the results which 
he ascribed to parallax, were explained by Bradley's 
great discoveries of the aberration of light, and the 
nutation of the earth's axis ; and it is remarkable that 
Hooke reasoned correctly on inaccurate observations, 
while Flamstead formed wrong conclusions from exceed- 
ingly correct results. 

James Cassini, in observing Sirius, attributed a paral- 
lax of six seconds to this star ; and La Caille, from ob- 
servations made at the Cape of Good Hope, supposed 
it four seconds. 

Piazzi, in researches pursued from 1800 to 1806, sup- 
posed that several of the fixed stars exhibit parallax. 
He assumes for Sirius nearly the same parallax as La 
Caille; for Procyon, three seconds; for Capella, less 
than a second. His conclusions are, however, given 
with great diffidence, and his object seemed to be, 
rather to call the attention of astronomers to a subject 
which had been for some time neglected, than to press 
bis opinions upon them with any thing like confidence. 

In all these observations made upon the stars, it must 



68 AWARD OF THE COPLEY MEDAL 

be confessed nothing like southern motion, had ever 
been suspected. 

Dr. Brinkley, in his first communication to the Royal 
Society on Parallax, in 1810, rated it for a Lyrae, at 
two seconds and a half. The Astronomer Royal, in 
endeavouring to confirm this result, has had no sati&- 
fiictory indiclttions of such a fact; and his general con- 
clusions, as you know, both firom observations made 
with a fixed instrument, and with the mural circle, are 
unfavourable to the existence of sensible parallax for 
any of the fixed stars; and he refers apparent parallax 
to the imperfection of the instrument with which the 
observations have been made, and offers, as a proof, the 
diminution of the indications, in proportion as instru- 
ments have become more delicate ; and estimating the 
Greenwich as superior to the Dublin circle, thus ac- 
counts for the difference of his results and those of Dr. 
Brinkley. 

This gentleman, in his last three papers on Parallax, 
has replied to all the arguments, and has endeavoured 
to overturn all the objections of the Astronomer Royal. 
He does not allow the superiority of the principle of 
the Greenwich instrument; and he shows the consis- 
tency of the Dublin instrument with itself, by thirteen 
summer solstices, for which observations on eighty-seven 
days were made, and which give the maximum of lunar 
nutation ff\BOy exactly what he had used for the sun, 
and very nearly the same result as that firom the stars; 
placing the permanent state of the instrument beyond 
all doubt. The results of two hundred and sixty-two 
observations on a Lyrse, in 1811, give the mean differ- 
ence between the summer and winter zenith distances 
at ^^32 ; and repeated observations made in the last 
ten years, give sensible parallax, though with less consis- 



TO DR. BRINKLBY. 69 

tency, for a Aquilae^ a Cygni, and AicturuB, but none 
for y Draconis. 

The minute accuracy with which Dr. Brinkley has 
investigated the subject^ can only be estimated by ac- 
complished mathematicians and astronomers. He has 
examined all Mr. Pond's results, reasoning upon the law 
of the aberration of light, the effects of refraction, and 
of differences of temperature, and has compared his 
own series of observations with those of other astro- 
nomers, and he seems entirely convinced of the accu- 
racy of his general conclusions. If any circumstances 
depending upon change of temperature, flexion of the 
instrument, or other causes of error existed, "Why," he 
says, " should they not be general for all the stars ?'* 
*' Why,** he asks, " should such causes exist for a Lyrae, 
and not for the pole-star, which shows no sensible pa- 
ralkx?" 

In his last paper, he makes some further corrections 
in the co-efficient of aberration and solar nutation, and 
his ultimate result is l'M4 for the annual parallax of a 
LyrsB. 

On the question of southern motion. Dr. Brinkley 
expresses himself with much more confidence than on 
that of parallax. He compares M. BesseFs, Mr. Pond's, 
M. Piazzi's, and the Dublin catalogues ; and after en- 
deavouring to prove a discordance in the Astronomer 
Royal's mode of applying the data in these catalogues 
to the question, he says, " from the weight of external 
testimony adduced, it will, I think, be readily con- 
ceded to me that the southern motion does not exist, 
and that it must be regarded as an error belonging 
to one or both of the Greenwich catalogues of ldl3 or 
1823." 

Such is the state of these two questions. 

They are not, however, questions of useless contro- 



70 AWARD OF THE COPLEY MEDAL 

versy, or connected with hostile feeKngs. The two rival 
astronomers seem equally animated with the love of 
truth and justice ; and have carried on their discussions 
in that conciliatory, amicable, and dignified manner, 
which distinguishes the true philosopher. I cannot give 
a stronger proof of this, than in stating that the Astro- 
nomer Royal was amongst the first of the Members of 
the Council to second and applaud the proposition for 
the award of this day. 

I have said that these questions are not questions of 
useless controversy, nor are they questions of mere cu- 
riosity. No important changes can take place in the 
sidereal system, without affecting the whole of astro- 
nomy: the fixed stars are, indeed, to space in the 
heavens, what land-marks, or the extremities of base 
lines, are to distances upon the earth ; and all our con- 
clusions upon the great problems of the system of the 
universe, have been formed upon the idea of the general 
permanency of their arrangements. 

With respect to parallax, it is not a little remarkable 
that Dr. Bradley, fi-om his varied and refined observa- 
tions with Graham's sector, concluded that a Lyrae 
could not possess a parallax of as much as 2'\ and that 
Dr. Brinkley's conclusions, from his most refined obser- 
vations, come far within these limits. Mr. Mitchell, 
likewise, from photometrical considerations, concludes 
that if the largest fixed stars are the nearest, and about 
the size of the sun, their parallax, taken from the quan- 
tity of light they emit, cannot much exceed one second ; 
and Mr. Gauss, in a conversation that I had with him 
this summer, informed me that he had drawn a si- 
milar conclusion, firom ascertaining the distance and size 
of the image of the sun upon the helioscope ; the new 
instrument that has been used with so much success in 
triangulation. 



TO DR. BRINRLET. 71 

There is one circumstance which seems to have per-, 
plexed Dr. Brinkley a little^ namely^ that some of the 
smaller stars seem to show a greater parallax than those 
of a larger apparent size : this, at first sight, might 
appear to throw some doubt upon the results ; yet it, 
perhaps, admits of explanation, on the idea that if the 
stars are disposed in groups or systems as Mr. Mitchell 
and Sir William Herschel believe, the bodies possessing 
the greatest masses, may be in the centre of these 
groups, and the smallest stars in consequence most 
contiguous to the largest It is to be regretted, that on 
the subject of parallax, no star has yet been observed 
absolutely in the zenith, which might easily be done 
in a part of the globe, for instance, under the equator, 
when almost precisely the same circumstances of tem- 
perature, moisture, and pressure of the atmosphere, 
would constantly exist. An instrument fixed on 
granite, or an aperture made in a solid stratum of 
rock, would destroy the probability of interference firom 
foreign causes, and reduce the problem to the simplest 
possible conditions. 

In waiting for new elucidations on these important 
questions (and no persons are more capable of giving 
ihem than the two distinguished astronomers now en- 
gaged in the discussion,) I cannot but congratulate the 
Society, that the state of scientific inquiry, and the 
number of scientific men, render it scarcely possible that 
any great problem can long remain unsolved, any con- 
siderable object of interest uninvestigated. No question 
is now limited to one observatory, to one country, or 
even to one quarter of the globe* While such men as 
Brinkley observe at Dublin, Bessel at Eonigsberg, 
Arago at Paris, Olbers at Bremen, Schumacher at Al- 
tona, and Gauss and Harding at Gottingen, astronomy 



72 AWARD OF THE COPLEY MEDAL 

must be progressive, her results cannot but become more 
refined. 

The observatories established by enlightened public 
patronage, at the Cape of Good Hope, and by private mu- 
nificence at Paramatta, in New South Wales, cannot &il of 
giving us almost anew sidereal world in the southern he- 
misphere. Already, Sir Thomas Brisbane has sent to the 
Royal Society an extensive catalc^e ; and we may ex- 
pect everything firom him that indefatigable zeal, ardour 
of pursuit, and intense love of the science can affonL 

With the increase of the popularity and the means of 
astronomy, &cilities for procuring the necessary in- 
struments, have likewise been greatly increased ; and it 
must be a gratifying circumstance to the lovers of 
science to know, that even on the Continent, extensive 
and accurate researches meet with no obstacle firom the 
want of proper apparatus; and though Germany 
cannot boast of a Ramsden, a Troughton, or a Dol- 
lond, yet it possesses a Reichenbach, and a Fraunhoier, 
whose instruments even the Astronomer Royal, I am 
sure, would examine with pleasure. 

All these circumstances ought to be subjects of 
congratulation to us, not of uneasiness; and if they 
produce any strong feeling, it should be that of emula- 
tion and of glory ; the desire of maintaining the pre- 
eminence which, since the foundation of the Royal 
Observatory, has belonged to us in this science. And, 
amongst the cultivators of the difierent branches of 
human knowledge, astronomers particularly, whose 
subject is the heavens, should be above the feelings 
of low, or even national jealousy: their results are 
for all nations, and for fiiture ages, and they require 
even for their perfection, the peaceful co-operations 
of philosophers in the remote parts of the globe. 



TO DR. BRINKLBY. 73 

I cannot give a more happy instance of this, than 
the manner in which the comet, of the shortest known 
period, of M. Encke, was observed by Sir Thomas 
Brisbane's assistants, in New South Wales, and the 
calculations of its return so fully verified. 

There is no more gratifying subject of contemplation 
than the present state and future prospects of astronomy ; 
and when it is recollected, what this science was two 
centuries ago, the contrast affords a sublime proof of 
the powers and resources of the human mind. The 
notions of Ptolemy of cycles and epicycles, and the 
moving spheres of the heavens, were then current 
The observations existing were devoted rather to the 
purposes of judicial astrology, than to the philosophy 
of ^'the heavenly bodies, to objects of superstition, 
rather than of science. 

If it were necessary to fix upon the strongest cha- 
racteristic of the superiority of modern over ancient 
times, I know not whether the changes in the art 
of war, firom the application of gunpowder, or in 
literary resources, from the press, or even the wonderful 
power created by the steam-engine, could be chosen 
with so much propriety as the improved state of 
astronomy. 

Even the Athem'ans, the most enlightened people of 
antiquity, condemned a philosopher to death for deny- 
ing the divinity of the sun ; and it will be sufficient to 
mention the idolatry and utter ignorance of the other 
great nations of antiquity, with regard to the laws or 
motions of the heavenly bodies. 

Take the most transient and simplest view of the 
science, as it now exists, and what a noble subject for 
contemplation I Not only the masses and distances of 
the sun, planets, and their satellites are known, but 

VOL. VU. E 



74 AWARD OF THB COPLEY MEDAL. 

even the weight of bodies upon their sur&ce ascertained, 
and all their motions, appearances, and changes pre- 
dicted with the utmost certainty for years to come, and 
even carried back through past ages to correct the 
chronology, and fix the epochas in the history of 
ancient nations. Attempts have been made to measure 
the almost inconceivable distances of the fixed stars : 
and, with this, what sublime, practical, and moral 
results ! The pathless ocean navigated, and in un- 
known seas, the exact point of distance from known 
lands ascertained. All vague and superstitious notions 
banished from the mind, which, trusting to its own 
powers and analogies, sees an immutable and eternal 
order in the whole of the universe, intended, after the 
designs of the most perfect beneficence, to promote the 
happiness of millions of human beings, and where the 
whole of created nature offers its testimony to the 
existence of a Divine aiul Supreme intelligence. 

I shall now conclude : Mr. Baily, you have been ao 
good as to undertake to transmit the medal to Dr. 
Brinkley ; no one is more capable of appreciating the 
high estimation in which his talents and character are 
held by the Royal Society. Assure him of our respect 
and admiration ; inform him, that presiding, as he does 
over another kindred scientific body, we receive his 
communications not merely with pleasure but with 
gratitude, and that we trust he will continue them, both 
for the advancement of astronomy, and for the increase 
of his own high reputation. 



75 



DI8COUR8B OF THB PBESIDENT, 
Anvitxbsast, Not. 30th, 1886. 
Cbaiaeter of Mr. William HioaiNS. — ^Awardof twoGovLBY Medak : 
one to M. Abago, F.R.S., M.R.A.S.P.,for his BificoTery of the Pro- 
perty poflsessed by Bodies in general to be affected by Magnetism ; 
and the other to Mr. Pbtbk Bah low, F.B.S., Professor at the Royal 
Military Academy at Woolwieh, for his Discovery of a Method of 
Coffieeting the Bnors of the Compass, arising from the Attraction of 
the Iron in a Ship. 

I HAVE, hitherto^ in concluding this painM part of my 
duty, (announcing the deaths,) usually taken some par- 
ticular notice of such of the deceased members, as have 
either contributed to your Transactions, or promoted, 
by their publications, the progress of science ; or have 
encouraged the pursuit by their personal exertions and 
social interest, at our meetings ; but upon this occasion 
I have scarcely more than the general sentiment of 
regret to offer. Many of the gentlemen whose names 
I have read to you were learned and ingenious men, 
and one of them a most laborious and industrious com- 
piler*: but however their loss may be regvetted by 
their friends, yet they can hardly be said to luwe been 
known sufficiently to the scientific world to call for 
particular notice before this body. I may except, 
perhaps, Mr. William Higgins, Professor of Chemistry 
to the Dublin Society, who published, nearly forty 
years ago, his Comparative View of the Phlogistic and 
Aniiphloffistic Theories, which contains some ideas of 
• Dr. Bees. 
E 2 



76 AWARD OF THE COPLBY MEDALS 

great importance with respect to what may be called 
the theory of definite proportions, or more commonly 
the atomic theory. He shows that bodies combine 
particle to particle, as 1 to 2 or 1 to 3, and so on ; and 
he gives many very happy instances of such combina- 
tion : but he brought forward no new ezperimentSt 
and endeavoured to establish a loose kind of dynamic 
hypothesis. His work, however, contains many curious 
and ingenious views, and it is impossible not to r^ret 
that he did not establish principles which belong to 
the highest department of chemistry, and that he 
suffered so fertile and promising a field of science to 
be entirely cultivated by others ; for though possessed 
of great means of improving chemistry, he did little or 
nothing during the last thirty years of his life. 

COPLEY BfEDALS. 

It is now my duty to announce to you the decision of 
your Council with respect to the avrard of the Copleian 
medals. 

. The medal of this year's donation they have bestowed 
on M. Abago, Fellow of this Society, and Member of 
the Royal Academy of Sciences of Paris. And another 
medal, which was not disposed of on a former year^r 
they have awarded to Mr. Peter Barlow, likewise a 
Fellow of this Society, and Professor in the Royal 
Military Academy at Woolwich. 

The discoveries and labours which your Council have 
made it their pleasure and thought it their duty to 
honour, by conferring on their authors the highest 
rewards of this Society, belong to the same depart- 
ment of science — magnetism, a department which has 
always claimed a considerable portion of your attention. 



TO M. AHAOO AND MR. BARLOW. 77 

both in its relation to philosophy and utility — to the 
laws and properties of natural bodies, and to naviga- 
tion, the great source of the power and prosperity of 
this mighty empire. 

That I may be able more distinctly to state the 
grounds of the decision of your council, I shall enter 
into a few historical details and general views on the 
subject, which I hope will not be unacceptable to our 
Fellows, not merely as setting forth the justice of the 
award, but as offering hopes of further discoveries, and 
as proving that though much has been done, more still 
remains to be effected for the distinct knowledge of ahe 
laws and relations of these mysterious phenomena. 

That wonderfid property by which a certain ore or 
stone attracted iron, seems to have been known from 
the most remote antiquity. The magnet was called by 
Aristotle, tear c^oxiiv '' n Xi0oc/' and its name has been 
by some derived from the supposed discoverer, by others 
from the town or city in Asia where it was said to be 
discovered. Various Greek and Roman philosophers 
have described its attractive powers; and Pliny, amongst 
others, in his usually animated manner, in speaking of its 
attraction for iron, says, " Domitrixque ilia rerum 
omnium materia ad inane nescio quid curret;" but 
its directive force, and consequently its use in naviga- 
tion, was wholly unknown to the ancients. 

We are uncertain when the polarity of the magnet 
was first applied to maritime purposes in Europe. The 
period is some time between 1100 and 1300. 

By some of the ancient authors the discovery is 
referred to Flavio Gioia, a native of Amalfi, in the 
kingdom of Naples, in 1300; by- others it is said tb 
have been brought from the Indies, by Marco Polo, in 
1240. The Chinese indeed pretend to have made the 



78 AWARD OF THE COPLBT MBDALS 

discovery some ages before it was known to the Euro- 
peans; but the natural vanity of this peofde renders it 
impossible to depend upon any statement not connected 
with authentic historical documents. 

That the compass did not point due norths (or its 
variation,) was discovered some time about the end of 
the 15th century, probably in the two great voyages to 
the eastern and western woilds, by Vasco de Gama and 
Christopher Columbus. The son of Columbus claiaied 
the merit of this discovery for his fiither in 1495. By 
odier writers, it b given to Sebastian Cabot, then in 
the employment of Henry VIL of England 

With respect to the change in the variation in the 
same place, and the knowledge of the dip of the needle, 
there is no such defect of historical precision ; both the 
dates and the discoverers are well known* The dip 
was ascertained by Robert Norman, our countryman, 
in London in 1581, and the change of variation was 
accurately demonstrated by Professor Gellibrand of 
Gresham College, in 1635. 

As the most important circumstances relating to the 
polar or directive force of magnetic bodies, were brought 
forward in this country, so likewise were the first just 
theoretical views respecting the circumstances of its 
communication and action. These views are owing to 
Dr. Gilbert of Colchester, who published his Latin trea- 
tise De MagnetCf in 1600. 

In this truly philosophical and original work, the 
author endeavours to prove that the phenomena of mag- 
netism are owing to the magnetic polarity of the earth ; 
that soft iron becomes a temporary magnet by the influ- 
ence of the earth : that in steel die magnetic property 
IS induced by the same cause with more difficulty, but 
that it is permanent ; and he explains the motion of the 



TO M. ARAGO AND MR. BARLOW. 79 

needle^ and the power of common magnets, by showing 
that opposite poles of different magnets attract each 
other in some definite ratio of their distance. He in- 
dulges, which could hardly be avoided in that age, in 
some vague hypotheses, and details some futile experi- 
ments; but notwithstanding this, his views display very 
extraordinazy powers of mind ; and though censured by 
his contemporary Lord Bacon, for endeavouring to solve 
the phenomena of gravitation by magnetic atttttction, 
yet his researches have a character of inductive reason- 
ing, perfectly in the spirit of the philosophy of that great 
man, who, had he studied his work with more attention, 
would have found in it numerous examples of his own 
sublime method of pursuing science — a contempt for 
Che speculative authority of the ancients, and an appeal, 
almost new in that time, to the laborious method of re- 
peated experiments. 

The general views of Gilbert were established, and 
his pardcular errors corrected by the early philosophers 
of this Society, by Wallis, Hooke, Halley, and Brooke 
Taylor. 

The diurnal variation of the needle was discovered 
by George Graham, in 1722 ; and the same ingenious 
artist first applied the vibrations of the needle as a mea- 
sure of magnetic intensity. 

That magnetic attractions and repulsions follow the 
law of the square of the distance, has been regarded as 
nearly demonstrated by the experiments of Lambert, 
Coulomb, and Robinson; and mathematical views of 
the theory of magnetism, upon the hypothesis of a single 
magnetic fluid, have been brought forward by Epinus 
and Robinson; and the highest refinements and pre- 
cision of the analytical method have been applied on 
the supposition of two fluids — the austral and die boreal. 



80 AWARD OF THE COPLEY MEDALS 

in two very recent Memoirs of M. Poisson, presented 
to the Royal Academy of Sciences at Paris. 

The hypothesis of magnetic, which so closely agrees 
with that of electric fluids, has been defended by simi- 
lar arguments, and illustrated by analogous experiments; 
and the connexion between the two classes of pheno- 
mena had been often observed and dwelt upon by phi- 
losophers. Beccaria had, indeed, from the magnetic 
effects produced by lightning, endeavoured to solve the 
magnetism of the earth by supposing it produced by 
electrical currents, which were likewise the cause of the 
Aurora Borealis and Australis. But these, and other 
opinions of the same kind, were supported only by vague 
analogies and insufficient facts, and, till the discovery 
of M. (Ersted, the true relations of magnetism and elec- 
tricity were unknown. 

I could, with pleasure, dwell on this discovery, and 
the immediate consequences of it in the develc^nnent 
of new and extraordinary results, and, would the time 
allotted to a discourse of this nature allow, I should have 
great satisfaction in describing to you the labours and 
the discoveries of various philosophers belonging to this 
and other learned Societies of Europe, and which have 
established, within the last five years, a perfectly new 
order of facts ; not less brilliant from their striking and 
unexpected results, than important in their relations 
and theoretical applications to other phenomena of na- 
ture. I cannot, however, quit this part of my subject 
without calling your attention to the manner in which 
these discoveries have originated and been pursued, as 
it offers the most remarkable instance upon record of the 
unity of the laws of nature— of the manner in which 
remote phenomena are connected together, and the 



TO M. ARAGO AND MR, BARLOW. -«! 

happy consequence of due attention to unexpected or 
common results. 

A feet, discovered by Galvani, and by him believed to 
be strictly physiological, investigated by the genius of 
Volta, was the origin of his wonderful pile or battery ; 
and this instrument, after its powers had been apparently 
exhausted in demonstrating new laws in electricity, and 
affording us new creations in chemistry,— altering our 
arrangements and systems, became, in the hands of the 
Danish philosopher, a source of novel and unexpected 
combinations, dirowing a light upon part of the corpus- 
cular philosophy which were before in absolute dark- 
ness. 

Though the labours of M. Arago, v^hich have been 
the object of the vote of your Council, cannot be con- 
sidered as immediate consequences of M. (Ersted's dis- 
covery, yet it is probable that they never would have 
been undertaken had not this discovery immediately 
excited the attention of their excellent author, who was 
amongst the first philosophers that endeavoured to in- 
vestigate, compare, and illustrate the facts of electro- 
magnetism. 

Coulomb imagined that all substances in nature were 
susceptible of magnetic attractions ; but from the nature 
of the bodies in which he supposed he had discovered 
these powers, it appeared probable that his results were 
owing to small quantities of iron in the material used. 

When it was found that magnetism was always a 
consequence of electrical action, various experiment^ 
vrere made with hopes of producing magnetic effects 
in other metallic bodies besides those. in which they 
have long been recognized; but it was found, with 
other metals, that all magnetic effect in electrical ex* 

£ 5 



82 AWARD OF THB COPLBT MBDALS 

periments were transient, disappearing i^ith the electrical 
cause. 

Till M. Arago's inquiries, iron, nickel, and cobalt, 
and their combinations, were the only species of matter 
apparently afiected by magnets. His experiments 
extend this property, under certain modifications, to all 
metallic substances, and it is said, though we have as 
yet no distinct details, to water, and varioos other 
bodies. 

M. Arago found that the extent of the vibrations of 
a magnetized needle, or the spaces through which it 
moved, were greatly diminished by holding over it 
a plate of copper; and by causing a plate of copper to 
revolve below it, the direction of the needle was soon 
changed; it began to turn round, and the velocity of 
its revolutions increased, till at last they became so 
quick as to be incapable of being numbered. M. An^o 
made the same trials with other metallic substances and 
with similar results, differing, as might be expected, in 
intensity ; and his experiments have been successfully 
repeated by Messrs. Uerschel and Babbage, and by Mr. 
Christie of Woolwich. Messrs. Herschel and Babbage 
have not only confirmed, but extended and illus- 
trated them by new inquiries. As action and reac- 
tion must in all cases be equal, it occurred to them 
to set in motion metallic plates by magnets, and 
they have been perfectly successful. A powerful horse- 
shoe magnet, made to revolve beneath metallic plates, 
sets them in motion, and ^ves them a great velocity of 
revolution. In these experiments, which I have had 
the satisfaction of witnessing, not only zinc, lead, tin, 
bismuth, and antimony have been used, but likewise 
mereury and carbon, in that state in which it is found 
in the retorts at gas manufiu^tories, and with similar 



TO If. ARAGO AND MR. BARLOW. 83 

results, though difiering conBiderably in degree* MM. 
Henchel and Babbdge, in a paper printed in the last 
part of the Transactions, have developed their re- 
searches and views in a very masterly manner; and 
those who wish to enter into this new field of science, 
cannot do better than study their experiments and 
their reasoning. 

It is for the discovery of this fact, — the power of 
various bodies, principally metallic, to receive magnetic 
impresrions, in the same, though in a more evanescent 
manner than malleable iron, and in an infinitely less 
intense degree,^--that your Council have awarded your 
medal; and you, I am sure, cannot but approve of 
their decision, for whether in its immediate relations or 
ultimate applications, there is no physical fact which 
has been made known, during the present year, that 
can, with propriety, be put in competition with it. 

By extending the empire of magnetism to a number 
of bodies, it removes much of what was mysterious and 
inexplicable in that department of science, and renders 
it a iHunch of the general philosophy of nature ; and 
when the new analogies between magnetic and elec- 
trical action, established by these phenomena, are con- 
sidered, there is much reason to hope that they may be 
altiikiately referred to the same caude with chemical 
affinirf, and possibly be found identical with the general 
quality or power of attraction of gravitation. 

Mr. Barlow has published several papers in the 
ThmsacHans of the Royal Society, which have established 
his character, both as a judicious and accurate experi- 
menter and able reasoner. These papers are, — 1. On the 
Effects produced on the Rates of Chronometers by the 
Proximity of Masses of Iron. — 2. On the Diurnal 



84 AWARD OF THE COPLEY MEDALS 

Variations of Magnetized Needles under a reduced 
Directive Power. — 3. On the Anomalous Magnetic 
Action of %nited Iron at different Temperatures. — 
4. On the temporary Magnetic Effects produced in Iron 
by its Rotation. And he has likewise given to the 
world a treatise, in which he has endeavoured to ex- 
plain the phenomena of magnetism by mathematical 
principles, according to an hypothesis, the same in its 
ground-work as that of the French philosophers, and 
in which the circumstances of the connection of 
magnetic powers with surface is demonstrated, and the 
whole subject treated with great ability and profound 
knowledge. 

The curious facts brought forward by Mr. Barlow, 
and the general accuracy of his reasoning, and the 
spirit of induction in his researches, would undoubtedly 
have claimed the attention of your Council, and 
might have led them to balance his merits with those of 
other contributors to your Transaction's; but their 
opinion was fixed, and their decision formed by a 
practical application of science, of great ingenuity and 
considerable utility. 

All persons, who have attended at all to the phe- 
nomena of magnetism since the time of Gilbert, know 
that masses of iron become magnetic by the action of 
the earth ; a bar of soft iron, for instance, held vertically, 
has its north pole uppermost, and attracts the needle in 
the same manner as the pole of the earth ; and any 
quantities or masses of iron, following the same law, 
exert an action on the needle proportional to the 
square of the distance, and of course destroy or di- 
minish, in a certain ratio, the action of the north pole 
of the earth. It is extraordinary that so important a 
circumstance as the action of the iron in a ship on the 



TO M. ARAQO AND MR. BARLOW. 85 

needle^ had not earlier and more strongly arrested the 
attention of navigators. Even Dr. Hallej, the most 
accomplished and profound philosopher that ever made 
long voyages, though he observed the effect, does not 
seem to have thought it worthy of correction, and that, 
.when making a set of minute observations on variations, 
he says, in his paper in the Transactions, '^ We know 
by experience how little the iron guns on boa^ a ship 
affect the needle." This, however, probably arose from 
the circumstances, that he was never in very high 
latitudes. Mr. Wales, the astronomer in Captain Cook's 
voyage, seems to have observed the fact, but Walker, in 
his Treatise an Maffnetism, was the first person who 
called th^ attention of nautical men to the circumstance. 
Captain Flinders brought it before the notice of the 
Admiralty, and Mr. Bain pointed out the fatal conse- 
quences attending it as a source of error in reckoning ; 
and lately the Arctic Expeditions have given the 
fairest and fuUest opportunity of determining the cir- 
cumstance, as may be learnt in the narrations of Cap- 
tains Ross, Sabine, Parry, Lyon, and other able 
officers ; and some correct general views on the sub- 
ject have been brought forward by M. Lecount. 

Mr. Barlow, after making a number of experiments 
on tlie phenomena presented by different laige masses 
of iron, and recurring to the principle, that the con- 
tiguity of a small mass, makes it equal or superior in 
power to larger masses, and that the attractions and 
repulsions diminish as the square of the distance, 
thought of two methods of correcting the errors arising 
from the magnetism of the iron in ships ; one by com- 
pensating, the other by doubling them, by means of 
small masses, or thin plates of iron, placed near the 
compass, and the relation of which to the magnetism of 



86 AWARD OF THB OOPLBY HBDAI^ 

the earth, the iron in the ship, and the needle, should 
be determined by experiments. 

The last method he has adopted in practice; and 
though, as M. Poisson has shown, it cannot be con* 
sidered strictly and mathematically precise, yet it may 
be regarded as sufficiently exact for all common pur- 
poses of navigation, and its utility has already been 
proved by the observations of Captain Baldey, Cap* 
tain Sabine, Captain Parry, Lieutenant Mudge, Lieu* 
tenant Foster, and various other able and enlightened 
officers. 

The Royal Society has always, since its first estab- 
lishment, given particular encouragement, and particular 
attention, to those departments of science which are 
strictly practical, and which offer the best vindication 
and the highest praise of the experimental and in- 
ductive method, bringing philosophy, as it were, from 
the heavens to the earth, and fixing her abode, not in 
visionary, splendid, and airy edifices, but amongst the 
resting-places and habitations of man. To point out a 
usefiil application of any doctrine or discovery, has 
always been their highest pride, and fortunately they 
have had many noble opportunities and examples; 
indeed, there is scarcely any instance of a considerable 
advance made in the knowledge of nature, without 
being soon connected with some tangible benefit or 
advantage, as light is almost always accompanied by 
heat, the illuminating by the productive and nourbhing 
principle. 

In conformity to the usages and feelings of the So- 
ciety, the Council has awarded the medal to Mr. Bar- 
low, who, by reasoning and experimenting upon a few 
simple facts, long known, but never applied, has founded 
a useful invention, tending to the perfection of an in- 



TO M. ARAQO AND MR. BARLOW. 87 

sdniineiiti the most important, perhape, to Britons^ of all 
thoae which have been the result of scientific principles, 
increasing the perfection of an art, which is not only 
one of the greatest sources of our power, but a bond of 
union amongst nations, securing their intercourse, and 
extending the progress of commerce, civilization, and 
refinement 

Mr. South, 

In transmitting this medal to M. Arago, assure 
him of the interest we take in his ingenious and im- 
portant researches ; and inform him that we wait with 
impatience for the continuation of his labours on this 
new and fertile subject. As one of our Fellows, his dis* 
coreries have the same interest for us, that they have for 
his brethren of the Royal Academy of Sciences, which, 
for more than a century and a half, has gone on encou* 
raging and emulating our labours. You and our worthy 
secretary* are recent examples of liberality on their 
part, and of the respect paid to British talent ; we, I 
trust, shall never be behind them in dignity and noble- 
ness of sentiment : far be from us that narrow policy 
which would contract the minds of individuals, and in- 
jure the interest of nations, by cold and exclusive sel- 
fishness; which would raise the greatness of one people, 
by lowering the standard of that of another. As in 
commerce, so in science; no country can become 
worthily pre-eminent, except in profiting by the wants, 
resources, and wealth of its neighbours. Every new 
discovery may be considered as a new species of manu- 
fiustofe, awaking novel industry and sagacity, and em* 
ploying, as it were, new capital of mind. When Newton 
developed the system of the universe, and established 

* Mr. Henchel. 



88 AWARD OF THB COPLBY MEDALS 

his own glory and that of his country on imperishable 
foundations, he might be regarded as giving a boon to 
the civilized world, for which no adequate compensation 
could ever be made ; yet, even in this, the most difficult 
and sublime field of discovery, Britain has been paid, if 
not fully, yet fairly, by the labours of Euler, La Grange, 
and, above all, Laplace ; perfecting the theory of the 
lunar motions and planetary perturbations, and afford- 
ing data of infinite importance in the theory and prac- 
tice of navigation. Fortunately science, like that nature 
to which it belongs, is neither limited by time nor by 
space. It belongs to the world, and is of no country 
and no age. The more we know, the more we feel our 
ignorance; the more we feel how much remains un- 
known ; and in philosophy, the sentiment of the Mace^ 
donian hero can never apply, — there are always new 
worlds to conquer. 

Mr. Barlow, 

I have great pleasure in presenting you with this 
medal, in the name of the Royal Society. Receive it 
as the highest mark of distinction which they have it in 
their power to bestow. You have already received 
marks of approbation, both at home and abroad, far 
more valuable in a pecuniary point of view, but no one 
which I think ought to give you more durable satisfac- 
tion ; for this reward has, I believe, never been made, 
except after dispassionate and candid discussion ; never 
to gratify private feelings, or to call for popular ap- 
plause; and, amongst the philosophers who have re- 
ceived it, are names of the very highest rank in science. 
We trust, both on account of the public good, and your 
own glory, that you will engage in, and accomplish. 



TO M. ARAOO AND MR. BARLOW. 89 

many new labours ; you have had not merely scientific 
success, but one still more gratifying to your heart and 
feelings, the idea that you have been useful to your 
country, and secured the gratitude of a body of men 
who are not tardy in acknowledging benefits. 



90 



DISCOURSE OF THE PRESIDENT, 

Annivbrsart, 1820. 

Charactera of Taylor Combb, Esq., and Sir Thomas Stamfoko 
Rafplbs. — ^Award of the Royal Medals to Mr. JounDalton, F.R.S., 
for his Development of the Theory of Definite Proportions, usually 
caUed the Atomic Theory of Chemistry ; and to Jambs Itory, Esq., 
F.R.S., for his various Mathematical Papen, published in the Philo- 
sophical Transactions. And on the Award of the Coplbt Medal to 
Jambs South, Esq., F.R.S., for his Observations on Double Stars. — 
With General Views on the Scientific History and Particular Merits 
of the Subjects for which the Prizes were given. 

I CANNOT pass over two of the names in this list without 
an expression of sorrow, at the loss the Society and the 
pablic have sustained in their death. Taylor Combe, 
Esquire, for many years one of your secretaries, was 
distinguished as a learned antiquarian, an elegant and 
accomplished classical scholar, and an excellent judge 
of works of art In his official situation in your 
service, he attended with great care and accuracy to 
the publication of the TransacHonSy till the state of his 
health interfered with his business and pursuits. In 
his public situation in the British Museum, he was 
most easy of access, and accommodating in promoting 
the pursuits of artists and scholars. His loss will be 
severely felt in the sister Society of Antiquarians, and 
lamented by all who were acquainted with the genuine 
worth of his character, the good nature and candour 
of his mind, and the kindness and simplicity of his 
manners. 



CHARACTBR OF SIR T. 8. RAFFLBd. 91 

Sir T. Stamford Raffles was not a contributor to 
your Transactions directly ; yet he was the occasion of 
many discoveries in zoology, botany, and physiology. 
His disinterested promotion of every branch of natural 
history ; his sacrifice of his fortune and his time to 
cdiections in this department of knowledge; the readi- 
ness with which he laid them open to scientific men, 
claimed the highest admiration. Occupying high situa* 
tions in our Empire in the East, he employed his 
talents and hk extensive researches, not in the exercise 
o( power or the accumulation of wealth, but in en- 
deavouring to benefit and to improve the condition of 
the natives, to found liberal institutions, and to estsr 
blish a permanent commercial intercourse between the 
colonies where he presided, and the mother country, 
which, whilst it brought new treasures to Europe, 
tended to civilize and to improve the condition of the 
inhabitants of some of the most important islands of 
the East. Neither misfortune nor pecuniary losses 
damped the ardour of his mind in the pursuit of know- 
ledge. Having lost one splendid collection by fire, he 
instantly commenced the formation of another: and 
having brought this to Europe, he made it not private, 
but public property, and placed it entirely at the dis- 
position of a new Association,* for the promotion of 
^Eoology, of which he had been chosen President by 
acclamation. Many of the Fellows of this Society can 
bear testimony to his enlightened understanding, acute 
judgment, and accurate and multiftrious information; 
and all of them must, I am sure, regret the premature 

* [The Zoological Society : of this association the author was one of 
the wannest promoters; he was concerned in forming the plan on which 
it was established, and the first address to the public, announcing it and 
folieitbig support for it, waa from his pen.] 



92 AWARD OF THE ROYAL MEDALS 

loss of a man who had done so much^ and from whom 
so much more was to be expected, and who was so truly 
estimable in all the relations of life. 

On our foreign lists of deaths, there is only one 
name. 

Padre Joseph Piazzi, formerly of Palermo, and late 
of Naples, whose name will descend to posterity, con* 
nected with one of the most important discoveries of 
the age, that of the planet Ceres ; and who, for nearly 
half a century, had pursued his favourite science with 
great ardour and success. He died, according to the 
course of nature, in old age, having etijoyed a glory» 
which in no respect disturbed his repose. 

ROTAL MEDALS. 

You will recollect. Gentlemen, that the Right 
Honourable the Secretary of State for the Home De- 
partment,* who, I am happy to state, has, upon all 
occasions, shown his zeal to promote the interests of 
science, and of the Royal Society, announced at your 
Anniversary dinner, last year, his Majesty's gracious 
intention of founding two annual prizes, each of the 
value of fifty guineas, to be at the disposal of the 
President and Council of the Royal Society, for pro- 
moting the objects and progress of science, by awaken- 
ing honourable competition amongst philosophers. 

As this foundation was announced in the true spirit 
of royal munificence, so it has been completed with an 
exalted liberality, worthy of our august patron. The 
two prizes are established in the forms of silver and 
gold medals, to be given for important discoveries or 
useful labours in any department of science ; and they 
* [Sir Robert PeeL] . 



TO MR. DALTON AND MR IVOBY. 93 

are laid open to learned and ingenious men of all 
countries, without any principle of narrow policy or 
national exclusion. 

In the first award of these royal medals, your Council 
have had some difficulties in their decision. Discoveries 
are sometimes made of great interest, wl^ich require 
time and new labours for their confirmation ; and when 
their importance is great and their bearings extensive, 
years even may pass away, before a full conviction of 
their truth can be obtained. Now, though vrithin the 
year just past, there have been more than one important 
discovery announced to the world, yet there are none 
which can be said to be, as yet, fairly and securely 
established. 

Your Council, therefore, have rather looked to labours 
which have been sanctioned by time, the importance of 
which is generally felt, though not sufficiently acknow- 
ledged; which may be said to have acquired their fiill 
authority only within a very short period, and which, 
consequently, may be considered as within the literal 
meaning of the foundation. 

I trust you will approve of the principle of the de- 
cision, and of the manner in which it has been made by 
your Council. 

They have awarded the first prize to Mr. John Dal- 
ton, of Manchester, Fellow of this Society, for the De- 
velopement of the Chemical Theory of Definite Propor- 
tions, usually called the Atomic Theory, and for his 
various other labours and discoveries in physical and 
chemical science. 

What Mr. Dalton's merits are, I shall briefly endea- 
vour to state to you, though it is impossible to do jus- 
tice to them, in the time necessarily allotted to this ad- 
dress. 



94 AWARD OF THB ROYAL MEDALS 

The brilliant and important discoveries of Black, Ca- 
vendish, Priestley, and Scheele, had added to chemistrj 
a great variety of substances before unknown, nuny of 
which had forms never before witnessed in the material 
world ; and the new and accurate logic of Lavoisier had 
assigned to many of them their just places in the 
arrangements of chemistry, and had estaUiaked the 
characters of most of them, as simple or compound 
bodies. Novel uses of these substances were ascer- 
tained, new combinations of them made, and their ap- 
plications to the purposes of common life, constantly 
extended by various distinguished chemists, in the dose 
of the last century ; but with respect to the weight or 
quantity in which the different elementary substances 
entered into union to form compounds, there were 
scarcely any distinct or accurate data. Persons, whose 
names had high authority, differed considerably in their 
statements of results, and statical chemistiy, as it was 
taught in 1799, was obscure, vague, and indefinite, not 
meriting even the name of a science. 

To Mr. Dalton belongs the distinction of first une- 
quivocally calling the attention of philosophers to this 
important subject Finding, that in certain compounds 
of gaseous bodies the same elements always combined 
in the same proportion ; and that when there was more 
than one combination, the quantity of the elements 
always had a constant relation, such as 1 to 2, or 1 to 3 
or to 4. He explained this fact, on the Newtonian doc- 
trine of indivisible atoms, and contended that the re- 
lative weight of one atom to that of any other atom 
being known, its proportions or weight, in all its com- 
binations, might be ascertained; thus making the statics 
of chemistry depend upon simple questions, in subtrac- 
tion or multiplication, and enabling the student to de- 



TO MR. DALTON AND MR. IVORT. 95 

duce an immense number of &ct8, from a few- well 
aathenticatedf accurate, experimental results. 

I have said that to Mr. Dalton belongs the distinction 
of first unequivocally calling the attention of philo- 
sophers to this subject ; but I should be guilty of his- 
torical injustice, if I did not state that various opinions 
and loose notions on. the same mode of viewing the com- 
binations of bodies, had existed before. And not to go 
back to the time of the Greek schools, to the Homoids 
of Anaxagoras, or to the Atoms of Epicurus, nor to 
those Newtonian philosophers who supported the per^ 
manency of atoms, and their uniform combinations, such 
as Keil, Freind, Hartley, and Marzucchi ; there may be 
found in the works of Dr. Bryan Higgins, Mr. William 
Ui^ins, and Professor Richter, hints or conclusions, 
bearing decidedly on this doctrine. Dr. Bryan Higgins, 
in his Experiments and Observations, relating to ace- 
tous acid, fixable air, dense, inflammable air, fire, and 
light, published in 1786, contends that elastic fluids 
unite with each other in limited proportions only; and 
that this depends upon the combination of their par- 
tides or atoms, with the matter of fire which surrounds 
them as an atmosphere, and makes them repulsive of 
each other ; and he distinguishes between simple elastic 
fluids, as composed of particles of the same kind, and 
compound elastic fluids, as consisting of two or more 
particles combined, in what he calls molecules, definite 
in quantity themselves, and surrounded by definite pro- 
pcMtions of heat. Dr. Bryan Higgins' notions have, I 
believe, never been referred to by Miy of the writers on 
the Atomic Theory. Mr. William Higgins' claims have, 
on the contrary, often been brought forward. Yet, when 
it is recollected, that this gentleman was a pupil and re- 
lation of Dr. Bryan Higgins, and that his work, called 



96 AWARD OF THE ROYAL MEDALS 

the Camparatwe View^ was published some years after 
the treatises I have just quoted, and that his notions are 
almost identical (with the addition of this circumstance, 
that he mentions certain elastic fluids, such as the com- 
pounds of azote, consisting of 1, 2, 3, 4, and 5 par- 
ticles of oxygen to one of azote,) it is difiScult not to 
allow the merits of prior conception, as well as of very 
ingenious illustration, to the elder writer. 

Neither of tlie Higgins attempted to express the 
quantities in which bodies combine by numbers ; but 
Richter has a claim of this kind. In his New F<nmda-' 
tions of Chemistnfj published in 1795, he has shown that 
when neutro-saline bodies in general undergo mutual 
decompositions, there is no excess of alkali, earth, or 
acid ; and he concludes that these bodies are invariable 
in their relation to quantity, and that they may be ex- 
pressed by numbers. 

Mr. Dal ton, as far as can be ascertained, was not ac- 
quainted with any of these publications, at least he 
never refers to them: and whoever will consider the 
ingenious and independent turn of his mind, and the 
original tone prevailing in all his views and specula- 
tions, will hardly accuse him of wilful plagiarism. But 
let the merit of discovery be bestowed wherever it is 
due ; and Mr. Dalton will be still pre-eminent in the 
history of the theory of definite proportions. He first 
laid down, clearly and numerically, the doctrine of mul- 
tiples ; and endeavoured to express, by simple numbers, 
the weights of the bodies believed to be elementaiy. His 
first views, from their boldness and peculiarity, met with 
but little attention; butthey were discussed and supported 
by Drs. Thomson and Wollaston ; and the table of che- 
mical equivalents of this last gentleman, separates the 
practical part of the doctrine from the atomic or hypo* 



TO MR. DALTON. 97 

thetical part, and is worthy of the profound views and 
philosophical acamen and accuracy of the celebrated 
author* 

Gay Lussac, Berzelius, Dr. Prout, aud other che- 
mists^ have added to the evidence in favour of the essen- 
tial part of Mr. Dalton's doctrine ; and for the last ten 
years it has acquired almost every month additional 
weight and solidity. 

Gentlemen, I hope you will clearly understand that I 
am speaking of the fundamental principle, and not of 
the details, as they are found in Mr. Dcdton's system of 
chemical philosophy. In many of these, the opinion 
of the composition of bodies is erroneous, and the num- 
bers gained from first and rude experiments, incorrect ; 
and they are given with much more precision in later 
authors on chemistry. It is in the nature of physical 
science, that its methods offer only approximations to 
truth; and the first and most glorious inventors are 
often left behind by very inferior minds, in the minutias 
of manipulation ; and Uieir errors enable others to dis- 
cover truth. 

Mr. Dalton's permanent reputation will rest upon his 
having discovered a simple principle, universally appli- 
cable to the facts of chemistry — ^in fixing the proportions 
in which bodies combine, and thus laying the founda- 
tion for future labours, respecting the sublime and 
transcendental parts of the science of corpuscular 
motion. His merits, in this respect, resemble those of 
Kepler in astronomy. The causes of chemical change 
are as yet unknown, and the laws by which they are 
governed ; but in their connexion with electrical and 
magnetic phenomena, there is a gleam of light pointing 
to a new dawn in science ; and may we not hope that, 
in another century, chemistry having, as it were, passed 
VOL. vn. F 



98 AWARD OF THE ROYAL MEDAL 

under the domimon of the mathematical sciences, may 
find some happy genius, similar in intellectual powers 
to the highest and immortal ornament of this Society, 
capable of unfolding its wonderful and mysterious laws. 

I could with pleasure enter into a history of Mr. Dal* 
ton's other labours in chemical and physical science, but 
it would be impossible to give even an intelligible sketch 
of them, without occupying too much of the time which 
ought to be allotted to the other business of this day. 
His experiments, on the equal expansion of elastic fluids 
by heat, are allowed to be accurate, and their results 
well founded. His notions on the nature of the atmo- 
sphere, the mixture of gaseous bodies, and the distribu- 
tion and communication of heat, and on the magnetic 
phenomena, display the resources of an ingenious and 
original mind ; and his essays on evaporation, and the 
force of vapour, and the tests for discovering water in 
air, have offered important practical applications ; but 
still their interest, though of a high kind, is inferior to 
that of the doctrine of definite proportions. 

I trust you will allow the justice of the decision of 
your Council, which has claimed for our countryman 
this first testimony of royal benevolence to science. * 

There is another motive which influenced them, and 
which I am sure will command your sympathy. Mr. 
Dalton has been labouring, for more than a quarter of a 
century, with the most disinterested view& With the 
greatest modesty and simplicity of character, he has re- 
mained in the obscurity of the country, neither askii^ 
for approbation, nor offering himself as an object of ap- 

* [By a writer of some note this decision of the Council of the Royal 
Society in awarding the first royal medal to Mr. Dalton, has been called, 
by some miacoountable perrersity of understanding, an insult to this dis- 
tinguished man.] 



TO MR. IVORY. 99 

plause. He is but lately become a Fellow of this So- 
ciety ; and the only communication he has given to you 
is one, compared with his other works^ of comparatively 
small interest ; their feeling on the subject, is therefore 
pure. I am sure he vrill be gratified by this mark of 
your approbation of his long and painful labours. It 
win give a lustre to his character, which it fully de* 
serves ; it will anticipate that opinion which posterity 
most form of his discoveries ; and it may make his ex- 
ample more exciting to othersf, in their search after 
useful knowledge and true glory. 

Your Council have awarded the second binary medal 
on the royal foundation, to James Ivory, M.A., for his 
papers on the Laws regulating the Forms of the Planets, 
on Astronomical Refractionsi and on other Mathe* 
matical Illustrations of important Parts of Astronomy. 

Every one who considers the glory derived to die 
Royal Society and to this nation, by the invention of 
the fluxional or differential calculus, and its application 
to the laws of the system of the universe, — every one 
who remembers the ascendency which for more than 
fifty years this Society enjoyed in the most sublime 
department of science, and the honour that would 
result from recovering it, will, I am sure, be pleased 
with this dedsiiHi of your Council, the object of which 
is, not only to reward a highly distinguished individual, 
bat likewise by setting forth his example, if possible 
to encourage others to pursue the same honourable 



All Mr. Ivory's most important mathematical labours 
have been communicated to the Royal Society, and 
published in your Transactions^ 

These communications are seven in number. Five^ 
f2 



100 AWARD OF THE ROYAL MEDAL 

including the first paper given in to the Society, 
in 1809, and the last published in 1825, are on the 
Forms which Spheroidal Bodies must assume, re- 
volving on their Axes, and acted on by the known 
Laws of Gravity and the Centrifugal Force. Of the 
two others — one is on a new Method of deducing the 
Approximation to the Orbit of a Comet, and the other 
of the Astronomical Refractions. 

One of the most important problems which exer- 
cised the skill of the illustrious author of the Principia^ 
was the effect of gravity and the centrifugal force in 
giving a peculiar form to a fluid mass ; which he cal- 
culated would correspond to the figures of the earth 
and the other planets. Maclaurin elucidated Newton's 
idea by a veiy refined and elegant synthetical process 
of reasoning. He determined generally the attractive 
forces of a homc^neous spheroid of revolution on a 
point placed within the solid or in its sur&ce; but 
there were still difficulties lefl, when the attracted 
point is placed without the solid, which were solved 
by the ingenuity of Legendre. The Marquis de la 
Place, in his Mechanique Celeste^ took a more enlarged 
view of the problem, and extended his method to all 
elliptical spheroids; but notwithstanding the refined 
principles and profound investigations of this illustrious 
geometer, and the elucidations of them attempted by 
his firiend and rival La Grange, there were some points 
unsolved, remaining in the application of the formulae 
and the generalization of the theorems, which awakened 
Mr. Ivory's attention, and which led him to examine 
the whole subject anew. In his first paper he considers 
the ellipsoid as homc^eneous, and treats the problem 
by the method of three co-ordinates. In his second and 
third papers he examines with great minuteness the 



TO MR. IVORt. 101 

methods of M. de la Place, and M. de la Grange. In 
his fourth paper he extends hb own method to all such 
spheroids as have their radii expressed by rational and 
int^ral fractions of three rectangular co-ordinates of a 
point in the surface of a sphere. And in the fifth he 
solves the problem in its generality, considering the 
body as a fluid homogeneous ellipsoid of revolution. I 
cannot pretend to give any idea of the mathematical 
resources displayed in these problems, and which even 
the most accomplished geometer could not render intel- 
ligible by words alone ; but I can speak of the testimony 
given by M. de la Place himself in their favour. That 
illustrious person, in a conversation which I had with 
him some time ago, on Mr. Ivory's first four communi- 
cations, spoke in the highest terms of the manner in 
which he had treated his subject; one he said of the 
greatest delicacy and difficulty, requiring no ordinary 
share of profound mathematical knowledge, and no 
common degree of industry and sagacity in the appli- 
cation of it 

Comets, before the foundation of this Society, were 
considered rather as objects of superstitious awe and 
vulgar astonishment, to be feared as portents, or ad- 
mired as wonders, than regarded as celestial phenomena, 
having a regular place and order in the solar system. 
The uncertainty of their appearances, their changes in 
brightness, the alterations in their most remarkable 
feature, the coma or tail, the rapidity and irregularity of 
their motions, sometimes nearly rectilineal, sometimes 
greatly curved, and sometimes retrograde, prevented 
even the most distinguished early astronomers, in- 
cluding Kepler, from forming any just opinions respect- 
ing their nature or their motions : and it was reserved 
for the unrivalled sagacity of Newton to show that they 



102 AWARD OF THE BOTAL MEDAL 

belonged to the same system, and were governed by tlie 
same laws as the planetary bodies, moving like them io 
conic sections but in different curves, depending opon 
the proportion of rectilineal velocity to the quantity of* 
deflection by gravitation towards the son. 

The triumph of the Newtonian views of the cometaiy 
system was considered as completed by the return 
of the comet predicted by Halley in 1759 ; but still 
great difficulties existed in laying down any general 
methods for calculating their times of return and 
places — from the circumstance of the earth and comet 
being both in motion — ^from the uncertain nature of 
the curve, and the disturbing causes which may act un- 
known to the observer, in space. Such celebrated men 
as Boscovich, Legendre, Lambert, La Place, and Gauss, 
have all contended with these difficulties with a success 
more or less partial. Notwithstanding the authority of 
such names, Mr. Ivory has not feared to enter into the 
same field of investigation, and he conceives that, con- 
sidering the orbit of a comet as parabolic, three geo- 
centric observations of its place are sufficient to furnish, 
by the method which he has proposed, elements for 
determining its course nearer the true ones, than they 
have been generally supposed, and a good first ap- 
proximation to the solution of a problem, which in 
some of its conditions must be indeterminate. 

I shall say a few words only of Mr. Ivory's paper on 
the Astronomical Refractions. 

The ancient astronomers had observed that there was 
a difference between the real and apparent places of 
the stars, arising from the refraction of light in passing 
through the atmosphere. Tyche Brahe by rude methods 
sought to free his observations from the effect of this 
irregularity; and the problem has occupied the at- 



TO MR. IVORY. 103 

tendon of Cassini, Eoamp, La Place^ Bessel, and 
Brinkley. 

A ray of light {rem a star, in passing through the 
atmosphere to the surface of the earth, is bent from its 
rectilineal course, by an attraction which depends 
principally on the density of the air, resulting from 
pressure and temperature. 

If the atmosphere had consisted only of a single 
elastic fluid, the temperature and pressure of which 
diminished according to a regular and uniform ratio 
from the surface of the earth, the problem of refractions 
would be an exceedingly simple one ; but unfortunately 
there are many causes which as yet are only impeiv 
fectly understood, that make the conditions much more 
complicated — the radiation of heat from the earth, the 
deposition of water, and the uncertainty whether the 
upper regions of the atmosphere are similar in com- 
position to the lower ones. 

Mr. Ivory's investigation is a very refined one. He 
has considered most of the uncertainties and all the 
difficulties of the subject; and if it is still left in 
an unfinished state, in making the corrections for stars 
near the horizon, it is not owing to any want of 
mathematical skill or acuteness of logic in this pro- 
found author ; but to the imperfection of our physical 
experiments which must furnish the data in all opera- 
tions of this kind. 

Whoever considers the fluctuations of the barometer, 
thermometer, and hygrometer in this climate at this 
^Bson, and the difierent efiects of radiation or cooling 
eauses in the nights, will have an idea of the difficulty 
of the subject, and the impossibility, it may be so called, 
^th the present tables of determining the true place of 
A star, within the limits of these changes. 



104 AWARD OF THE ROTAt HEDAt. 

Your Council of this year, as you know, Gentlenien;, 
contains several distinguished mathematicians, who were 
decisive in claiming this award for Mr. Ivory, and I 
trust your approbation will sanction their decision* I 
may likewise apply to Mr. Ivory praise of the same 
kind as that which I had the honour of applying to Mr. 
Dal ton. He has pursued science with the same dis- 
interested zeal, and as it were, with a pure affection for 
the cause of truth. He has received no emoluments, 
and occupied no places of dignity. He has quietly and 
unobtrusively brought forward his labours — they have 
had no popular object, and only a high scientific aim ; 
being intelligible only to a few superior minds, and he 
has waited for the slow progress of time to ensure him 
their confidence and approbation. ^ 

I feel the highest satisfaction in anticipating that this 
award may renovate the activity of the Society upon 
this department of science, and that it will return, '^ ve- 
teris vestigia flammse," with new ardour to its so long- 
neglected fields of glory. 

Whether we consider the nature of mathematical 
science or its results, it appears equally amongst the 
noblest objects of human pursuit and ambition. Arising 
a work of intellectual creation, from a few self-evident 
propositions on the nature of magnitudes and numbers, 
it is gradually formed into an instrument of pure reason 
of the most refined kind, applying to and illustrating 
all the phenomena of nature and art, and embracing the 
whole system of the visible universe: and the same 
calculus measures and points out the application of 
labour, whether by animals or machines — determines 
the force of vapour, and confines the power of the most 
explosive agents in the steam engine — ^regulates the 
forms of structures best fitted to move through the 



AWARD OF THE COPLBY MEDAL. 105 

waves — ascertains the strength of the chain-bridge 
necessary to pass across arms of the ocean — ^fixes the 
principles of permanent foundations in the most rapid 
torrents — and leaving the earth filled with monuments 
of its power, ascends to the stars, measures and weighs 
the sun and the planets, and determines the laws of 
their motions, and even brings under its dominion those 
cometaiy masses that are, as it were, strangers to us 
wanderers in the immensity of space ; and applies data 
gained from the contemplation of the sidereal heavens 
to measure and establish time and movement, and mag- 
nitudes below. 



COPLET MEDAL. 

There is another annual medal. Gentlemen, on which 
I have to announce to you the decision of your Coun- 
cil, that founded on the donation of Sir Godfrey Cop* 
ley, Bart This, for a long while, was the only mark 
of distinction which you had to bestow : and when the 
illustrious names to whom it has done honour are con« 
sidered, and the great and extraordinaiy advances in 
natural knowledge with which the award has been con- 
nected, it will, I trust, continue to retain all its dignity, 
as a mark of our respect, and all its importance as a 
pure honorary reward. It has been voted this year to 
James South, Esq., Fellow of the Royal Society, for 
his paper of Observations of the Apparent Distances 
and Positions of four hundred and fifly-eight double 
and triple Stars, published in the present volume of the 
Transactions. 

The illustrious Florentine philosopher to whom we 
owe the discovery of the telescope, and all the first pure 
experimental results in natural philosophy, was, as I 
f5 



106 AWARD OF THE COPLEY MEDAL 

mentioned in a former discourse^ the author of the idea 
of attempting the discoyery of the parallax of the fixed 
stars by the observation of double stars, Galileo sup- 
posing the fixed stars to be analogous to our sun in 
nature and magnitude^ but at immense distances from 
us, and firom each other, proposed the observation of 
two stars of different apparent sizes, and seemingly very 
near each other, at the summer and winter solstice, 
giving the two extremities of the earth's orbit, with the 
hope that a difference might be observed in their posi- 
tion, indicating parallax. 

This method was insisted on by Dr. Wallis, but not 
put in practice, as the questions respecting the disco- 
veries of Newton soon occupied, almost exclusively, 
the attention of philosophers. 

Dr. Bradley and Mr. Molyneux, in endeavouring to 
follow the observations of Hooke to determine the pa- 
rallax of fixed stars near the zenith, by an instrument 
constructed by Mr. Geoi^e Graham, and more accurate 
than had ever before been made, believed they observed 
a proper and considerable motion of y Draconis : and 
Dr. Bradley, after Mr. Molyneux's death, pursuing the 
same inquiries firom 1727 to 1748, was convinced of an 
apparent motion of this, and of other fixed stars. 

The Rev. Mr. Michell, in a very ingenious and ela^ 
borate paper published in the PMbsaphical Transactions 
for 1767, developes some new and very ingenious views 
of the sidereal system. He supposes that stars may be 
arranged in groups ; and to whatever cause this may be 
ovring, whether to their mutual gravitation, or to some 
other law or appointment of the Creator, he supposes 
that some of them may act to others the parts of secon- 
dary to primary planets, or of planets to the sun. 

Fortunately for astronomy Sir William Herschel took 



TO MR. SOUTH. 107 

up this subject in 177.9, principally with the hope of 
discovering parallax; but though he fiuled in this ob- 
ject, yet his observations led to new and most important 
discoveries, confirming and extending the ideas of Mr. 
Michell, and advancing, in a most extraordinary man- 
ner, our knowledge of the system of the universe. 

The results of Sir William Herschel's observations 
firom 1779 to 1784, were published in two catalogues in 
the PhUasap/ucal Transactions for 1782 and 1785, and 
consist of descriptions and measures of seven hutidred 
and two double and triple stars. The labour of re- 
examination was undertaken and executed by him in 
1801, 1802, 1803, atid 1804, after a lapse of twenty 
years, and the changes observed or suspected, were re- 
corded in two other papers published in the volumes of 
the Society for 1802 and 1804. In 1816 a second exa- 
mination of the measures was commenced by Mr. Her- 
schel, a son worthy of his father, and some progress 
made in it ; and Mr. South being in possession of cer- 
tain instruments, perfected by the labour and skill of 
Mr. Troughton, became associated with Mr. Herschel 
in these researches, which were recommenced in March, 
1821, and carried on by Mr. Herschel and Mr. South 
jointly till 1824, and their results published in an ex- 
tensive memoir, containing their observations of three 
hundred and eighty double or triple stars in the Trans- 
actions of that year. 

By these ol^ervations many of the conclusions and 
suspicions of Sir William Herschel were proved, the 
existence of binary systems in which two stars appear 
to perform to each other the office of sun and planet 
was distinctly shown, and the periods of rotation of 
more than one such pair determined in a manner ap- 
proaching to exactness ; the immersions and emersions 



108 AWARD OF THE COPLBY MEDAL 

of Stars behind each other were demonstrated, and real 
motions amongst them detected, rapid enough to be* 
come sensible and measurable in very short intervals of 
time. 

These important researches were continued by Mr. 
South, at Blackroan Street, and at Passy, near Paris, in 
1823, 1824, and 1825, and their results form the first 
part of the Philosophical Transactions for this year. 
The work which, as I have already mentioned, is the 
object of the award of your Council. 

These laborious and accurate observations, which fill 
three hundred and ninety-one pages, relate to four hun- 
dred and fifty-eight double and triple stars: of these 
one hundred and twenty-three were discovered and 
observed by Sir William Herschel, one hundred and 
sixty were discovered by Mr. South, at Passy, and the 
remaining one hundred and seventy-five by other astro- 
nomers. 

There are some very curious, I may say almost won- 
derful, instances of proper motions of stars, of occulta- 
tions of stars by each other, proved in these pages ; but 
the most important result is, the apparent connexion of 
stars in binary systems of rotation, which seems to render 
it probable that the law of gravitation extends to this 
part of the universe. There are forty-three phenomena 
of this kind observed by Mr. South : in some the mat- 
ter is placed he thinks beyond all possibility of doubt; 
whilst in others, the motion being less rapid, observa- 
tions at a future and more distant period are required 
to establish the fact with security. 

As amongst the most int^^sting of the double 
stars, we may enumerate the following : — c Bootis, y Viiv 
ginis, a Geminorum, (or Castor), a Coronse Borealis^ 



TO MR. SOUTH. 109 

ii Cassiopeiae, 61 Cygni^ K Ursae Majoris, and 70 Ophi- 
uchL 



€ BootU. — Large white^ small blue ; distance, 3 seconds 
and 4-tenths ; period, about 822 years — motion di- 
rect* 

y Fir^'ni>.— 8th and 8-^ magnitudes; both white; dis- 
tance, 3 seconds and 3-tenihs; period, about 540 
years — ^motion retrc^rade.f 

o GeminoTum {or Castor). — 3rd and 4th magnitudes ; 
both white; distance, 4 seconds and 8-tenths; pe- 
riod, about 373 years — amotion retrograde. 

<r CorofUB BoreaUs. — 6th and 8th magnitudes ; distance, 
1 second and 6-tenths; period, about 169 years — 
motion direct 

If CasMpeuB. — 6th and 9th magnitudes; large red, 
small green ; distance, 9 seconds and 9-tenths ; pe- 
riod, about 700 years — motion direct 

61 CygnL — ^7 th and 8th magnitudes; both white; dis- 
tance, 15 seconds and 4-tenths ; period, about 493 
years — motion direct 

5 UrMR Majoris. — 6^ and 7 th magnitudes ; both white ; 
distance, 2 seconds and 4-tenth8; period, about 71 
years — motion retrograde. 

70 OphiuckL — 8th and 8-^ magnitudes; distance, 4 se- 

* of. sp. t np. sf. 



110 AWARD OF THB COl»LEt MEDAL 

conds and 8-tenths ; period, about 53 years — amotion 
direct. 

TRIPLE STABS. 

12 Lynci8.—K of the 7th, B of the 7^, and C of the 9th 
magnitudes ; of AB, distance, 2 seconds and 5-tenths; 
of AC, 9 seconds and 2-tenths; period of AB (or 
the close pair) 646 years — motion retrograde ; whilst 
AC (or the distant pair) have not materially changed. 

g Scarpa. — A of the 7th, B of the 7th, and C of Ae 
9th magnitudes ; of AB, distance, 1 second and 4- 
tenths ; of AC, 7 seconds. 

The close pair, AB, has suffered no alteration since it 
was observed by Sir William Herschel, in 1782. 

Whereas the period of the distant pair, or AC is pro- 
bably about 1406 years — amotion retrograde. 

Two instances are furnished in which occultations of 
stars by others have occurred; they are S Cygni, and H^ 
Herculis; and this fact is confirmed by the inquiries 
of Professor Struve, at Dorpat; and some additional 
confirmations of the proper motions of other stars have 
been recently made by Dr. Brinkley, now Bishop of 
Cloyne, at Dublin. 

When the importance of an acquaintance with the 
position of the fixed stars in the heavens is considered, 
on the accurate knowledge of which all our data in re-* 
fined astronomy, and many of those in practical navi- 
gation, depend : and when the new and sublime views 
of the arrangements of infinite wisdom in the starry 
heavens, resulting fi'om these inquiries, are considered, 
you will, I am sure, approve of this vote of your Council. 

Mr. Herschel has, on another occasion, enjoyed the 



TO MR. SOUTH. Ill 

honour of the Copley medal: and a like mark of your 
respect is surely due to his feUow'-Iabourer^ who> having 
provided his own instruments, at a great expense, has 
employed them at home, and carried them abroad, 
trusting entirely to his own resources, and pursuing his 
&yourite science In the most disinterested and liberal 
manner, communicating all his results to this Society. 

Hiere is a reason, likewise, which must be almost 
considered as personal. Whoever has seen the methods 
in which observations of this kind are conducted, must 
be aware of the extreme fittigue connected with them, 
of the watchful and sleepless nights that must be de- 
voted to them, of the delicacy of manipulation they re* 
quire, and of the sacrifices of ease and comfort they 
demand I 

In dwelling upon this award, there is another circum- 
stance to which I cannot but allude ; it fixes, as it were, 
the perfection and delicacy of the instruments employed, 
without which all labour would be in vain. In these 
instances of research, man, as it were, conquers space, 
and triumphs over time; and by almost infinitely 
minute and delicate resources, by aids which may be 
called microscopic, contemplates and embraces the 
grandest objects: and if the pure, mathematical sci- 
ences obtain their great truths by the strength of the 
human intellect, &cts of this kind on which they must 
reason, are owing to the wonderful perfection of the 
human eye and hand, applied to produce combinations, 
which measure portions of space, formerly believed im- 
measurable by human powers. 

Mr. South, 
I have great pleasure in presenting to you this medal. 
Receive it as the ancient olive crown (to use a metaphor 



112 AWARD OP THE COPLEY MEDAL. 

taken from the Olympic conquerors) of this Society; 
and it has a higher claim to this appellation, as belong- 
ing to arts of peace, which can only benefit mankind. 

Researches of the kind, for which you receive this 
reward, if they have not the immediate effect or striking 
popularity of some other labours, yet are secure in 
their value, and sure of endurance. Other pursuits and 
successes may be connected with the passions, preju- 
dices, and uneasy feelings of the day. These will out- 
live them; they require time for their complete deve- 
lopment; they appeal to time for the meed of gloiy 
belonging to their discoverers. 

Mr. South, your name is committed, as it were, to 
posterity, for more than ten centuries, in the largest pe- 
riod of revolution assigned to a double star : and it must 
be some satisfaction to you to know, that at so immense 
a distance of time, should our records remain, like those 
of Hipparchus and Ptolemy, when the brazen instru- 
ments with which you have observed are decayed, and 
the structure under which we stand crumbled into dust, 
your name is sure of being recalled with that of the two 
Herschels, by some accurate observer of the heavens. 

I trust that this motive, as well as the nobler one of 
utility, will induce you to pursue and persevere in those 
researches, and steadily to apply your mind, your undi- 
vided attention, to this one great object, secure that you 
will reap abundant fiiiits from your labours, and that 
you will enjoy the pure pleasure resulting from the con- 
viction, that you have increased the stores of human 
knowledge, and laboured not merely for those who are 
now living, but likewise for future generations. 



[The following notices of three of the most difitingnished chemists of 
modem times, and of Newton, the two Bacons, and of Pliny, may, it is 
hoped, be considered as deserving of a place in the author's Collected 
Works, although they are merely hasty sketches ; and the more so, per- 
haps, on this account, as being thereby most likely to exhibit and ex- 
press his current habitual feelings and sentiments on scientific excellence, 
the methods of science, and the peculiar merits of the individuals.] 



115 



[SKETCH OF THE CHARACTER 
OF DR. PRIESTLEY.*] 

Stimui«at£d by the examples of Dr. Black and Mr. 
Cavendish, Dr. Priesdey, about the year 1770, applied 
himself with intense ardour to experiments on the 
subject of air. By a constant application of the com- 
binations and agencies of the various chemical sub- 
stances, he discovered oxygen gas, nitrous gas, nitrous 
oxide, and light carburetted hydrogen; and by using 
the mercurial apparatus, he exhibited several of the 
acids in an aeriform state, and demonstrated their 
properties. As a discoverer. Dr. Priestley stands in 
the highest rank ; and it is scarcely possible to advance 
a step, or to perform a process in pneumatic chemistry, 
without having recourse to his methods, and making 
use of substances he first exhibited. His activity was 
unceasing; and in physical science all his exertions 
were crowned with success. His experiments, though 
neither accurate nor minute, were almost always upon 
subjects of importance ; he made up for the defect of 
his manipulations by the rapidity of execution, and the 
novelty of his methods. He prepared the way for 
more accomplished chemists; he furnished them with 
matter of inquiry ; and, in the true spirit of liberality, 
offered to the world all his treasures of science. He 
was as the miner, who discovers hidden riches, and 
furnishes them in the unwrought state to the cunning 
* [From a Chemical Lecture delirered in ISIO.] 



1 16 SKETCH OF THfi CHARACTER 

artist; the ore that he brought to light Vfsa crude, but 
it was precious and useful. To theory Dr Priestley 
paid but little attention ; and his hypotheses were 
rapidly formed, and relinquished with an ardour almost 
peurile. His chemical writings are principally narra- 
tions of facts ; and though the style and arrangement 
are defective, from hasty composition, yet it is im- 
possible not to be amused and interested by his details. 
They are copious, dbtinct and satisfactory'; and the 
manner in which they are pursued leaves a very favour^ 
able impression of the simplicity, the ingenuousness, and 
candour of his mind. 

Dr. Priestley was a discoverer before he was a 
chemist. In a letter, which I received fit>m him a 
few months before his death, he makes this statement, 
in his usual una£Pected manner. It is easy, therefore, 
to find a reason for the occasional incorrectness of 
his views. Throughout the whole course of his life 
his attention was never undivided. His mornings 
were devoted to experiment; his evenings to politi- 
cal, theological, or metaphysical inquiries. He is an 
example how much may be done by small means, when 
applied with industry and ingenuity, and how easy it 
is, in some instances, to enlarge the boundaries of 
chemical knowledge; and how much more real and 
permanent glory is to be gained by pursuing the 
immutable in nature, than the transient and capri- 
cious in human opinion. When Dr. Priestley's name 
is mentioned in future ages, it will be as one of the 
most illustrious chemical discoverers of the eighteenth 
century. 

[In the next lecture, the subject of which was nitrous 
gas, the author gives some further particulars of Dr. 
Priestley ; and especially of the kind of apparatus 



OF DR. PRIESTLEY. 117 

used by him. Having observed that he '^knew no 
book so likely to lead a student into the path of dis" 
covery as Dr. Priestley's six volumes upon air," he 
continues : — "] 

His most important experiments were made with 
apparatus of the most simple kind. His grandest and 
most expensive instrument, like that of Dr. Hales, 
was a gun-barrel. He used phials and bent tubes 
for retorts; a wash-hand basin often served him for 
a pneumatic trough, and instead of porcelain tubes he 
employed tobacco pipes ; and with this simple ma- 
chinery he discovered a greater number of new sub- 
stances than any philosopher of the last century. 

[The next paragraph of the lecture, describing the 
manner in which nitrous gas was discovered by Dr. 
Priestley, may be considered deserving of insertion, as 
an example of the manner in which he made his dis- 
coveries, and as displaying the acumen of intellect of 
Mr. Cavendish.] 

Dr. Hales has mentioned in his statical essays, that, 
during the solution of a mineral, which he calls Walton 
Pyrites, and which must have been a common pyrites, 
he procured air, which, when mixed with common air, 
gave a turbid red fume. Dr. Priestley, in mentioning 
to Mr. Cavendish that he wished much to witness the 
phenomenon, but that he despaired of ever procuring 
Walton Pyrites, was advised by Mr. Cavendish to try 
any pyrites, or metallic substances; for he had no doubt 
that the properties of the air depended upon the spirit 
of nitre, the nitrous acid, and not upon the substance 
dissolved. This hint led to the knowledge of the 
properties of a new elastic fluid : Dr. Priestley first 
procured nitrous air by dissolving brass in nitrous 
acid 



118 SKETCH OF THS CHARACTER 



[OF SCHEELE.] 

I have mentioned Scheele as an admirable experi- 
menter. As^ in the last lecture, I endeavoured to do 
justice to the philosophical labours of Cavendish and 
Priestley, I shall, with the same kind of feeling, refer 
to the exalted character of the only foreign philosopher 
of the last century, whose merits as a discoverer can 
be at all put in competition with those of our country- 
men. 

Scheele offers an extraordinary instance of the power 
of genius to conquer difficulties, and to create resources 
of its own. Bom in a country town in Sweden, with- 
out friends, and without fortune, he seemed, by a dis- 
position which may be called almost instinctive, to have 
pursued the study of chemistry. He was brought up 
as an apothecary and druggist ; and led, by the circum- 
stances of his business, to attend to some of the chemi- 
cal qualities of substances employed in pharmacy, he 
instituted a train of investigations, which gradually led 
to discoveries of the noblest kind. Scheele, amidst the 
labours of an unprofitable occupation, found means of 
exalting and extending the more refined parts of 
chemistry. His days were devoted to a laborious 
business; his nights to solitary study. Usu^ the 
common apparatus of pharmacy, he performed the 
most delicate manipulations, neither seeking fame nor 
profit by his labours; for, till he became acquainted 
with Bergman, he was ignorant of the honour whidi 
would result firom discoveries: neither seeking fiune 
nor profit, he pursued science, because his mind was 
imbued vrith an unquenchable desire for truth. No- 
thing could repress the ardour of his mind, nor damp 



OF 8CHSELE. 119 

the fire of his genius; and his short life was a career of 
enterprise and of glory. Scheele made known at least 
thirteen new bodies ; and his chemistry may be called 
almost his own creation. His theories were formed 
with boldness, but he attached no importance to them 
except as the mere Unks for the connection of facts. 
He was the &ithful disciple of the school of Bacon and 
of Newton. 

At the time that Scheele began his chemical labours, 
about 1772, Beigman, professor of chemistry at Upsal, 
was the great scientific luminary of Sweden. He had 
distinguished himself by some very profound investiga- 
tions concerning chemical attraction, and had ascer- 
tained some important facts respecting metallic bodies 
and neutral salts. The manner in which Beigman 
brought forward Scheele, is highly honourable to the 
scientific character of the country. He wrote a prefiuse 
fi>r his first work, was his firiend and protector; and, 
relinquishing the venerable authority of his chair, he 
became the disciple of a young man as yet unknown to 
the world. It has been said of Bei^man, that ^his 
greatest discovery was the discovery of Scheele.' It 
may, perhaps, Ukewise, be said, that his greatest 
glory, was the glory of raising and exalting merit, even 
tbou^ it was in acknowledging his own inferiority. 
jSuch examples are very rare. There are few instances 
of such sacrifices of selfish feelings ; and that they should 
be &ithfiilly recorded, is necessary for the honour of 
human nature, aad for demonstrating, to use the lan- 
guage of Bacon, borrowed fix>m Scripture, that ^ wisdom 
is justified of her children.' 

[In another lecture, in which the author notices the 
character of Scheele, in similar terms of highest praise 
and admiration, he says: — "] 



120 SKETCH OF THE CHARACTER 

I have been drawn into this eulc^um, not merely 
because it is fully deserved, but because the example of 
Scheele demonstrates what great effects may be pro- 
duced by small means ; how little is required to extend 
the empire of knowledge, when genius is assisted by in- 
dustry. 



[OF PLINY THE ELDER.*] 

[After having remarked that the philosophy of Rome 
was little more than an imperfect copy of that of 
Greece, the author proceeds :] 

The only Roman who really deserved the title of an 
investigator into natiure, was the elder Pliny. This 
illustrious person possessed the highest degree of in- 
dustry, and an ardour in the pursuit of knowledge, 
which no difficulties could repress. He considered all 
the productions of the earth as worthy of attention, 
either for their order, their beauty, their uses, or rela- 
tions to man. Possessed of such requisites for dis- 
covery, he was still deficient in the great characteristics 
of a strong mind and a philosophical spirit Endowed 
with a simple heart, and, apparently incapable of de- 
ceiving, he believed almost whatever was related to him ; 
doubt seemed to be a stranger to his understanding. 
He beheld things in their obvious forms, with delight 
and with wonder ; and, satisfied with what he saw, he 
seldom attempted to refer effects to their causes. En- 
dowed with none of the high elements of reason, — ^with 
none of those restless workings of the imagination, 
which produce new combinations of ideas, new truths, 
and new inventions, — ^he was, nevertheless, a minute 
* [From an early Lecture on Geology, about 1804.] 



OF BACON. 121 

observer and a faithful historian, but neither an experi- 
mental philosopher, nor a man of genius." 



[OF LORD BACON.»] 

[Of Lord Bacon, speaking of the period in which he 
lived, the author remarks:] 

Many scientific persons, before Bacon, had pursued 
the method of experiment in all its precision, — many 
had dared to despise the logic and forms of the ancients ; 
but he was the first philosopher who laid down plans 
for extending knowledge of universal application ; who 
ventured to assert, that all the sciences could be nothing 
more than expressions or arrangements of £acts; and 
that the first step towards the attainment of real dis- 
covery, was the humiliating confession of ignorance. 
Bacon was prepared, by nature, by education, and by 
bis habit of study, for effecting the great revolution in 
philosophy. His knowledge was extensive; his in- 
stances were copious ; his genius was equally capable of 
developing the lighter and more profound relations of 
things. He possessed a strong feeling, but it was uni- 
formly directed by reason : he was gifted with a vivid 
imagination; but it was tempered and modified by a 
most correct taste and judgment The influence of 
rank and of situation assisted his views. The public 
was prepared to receive them ; and he was enabled to 
advance his opinions, in full confidence that they would 
be adopted with reverence in his own time, and that 
they would carry his memory into fiiture ages with 
gpreat and with unchanging glory. 

[He immediately adds,] 

* [From the same Lecture.] 

vol*, vn. G 



122 SKETCH OP THE CKARACTER 

The pursuit of the aew method of inTestigatkHi, la a 
very short time, wholly altered the face of every depart- 
ment of natural knowledge ; but its influence was in no 
case more distinct than in the advancement of geology 
and chemistry. Though much labour had been be- 
stowed upon these extensive fields of investigation, they 
had hitherto, as it has been seen, been little productive. 
Speculation had been misplaced, observadoa confined, 
and experiment principally directed, rathec towank im- 
possible, than to practical things. In the novel system, 
hypothesis was exploded, except as a guide to actual 
trials; combinations of thought were considered as 
truths, only when conformable to nature, and not whea 
they merely expressed the ci^rices of the imagination ; 
and those inquiries only were considered as valuaUe, 
which were made upon the hidden, sensible properties 
of things, and upon the existing relations of £Eusts. 



[OF THE ELDER BACON.*] 

[Having pointed out that the elder Bacon was one of 
the first persons who applied himself to experiment in 
the dark period in which he lived, for the purpose of 
the advancement of science, and under the guidance of 
philosophical views ; and that in his gseat work, he ccm* 
fessed he had gained the foundation of his knowledge 
fi^m the Arabian writers, the author adds :] 

This great man evidently studied nature, and the 
productions of the earth, with the views of a philo- 
sopher ; — ^but his knowledge was so superior, as to be 
unintelligible in the age in which he lived; the wonders 
produced by chemistry, were referred by the people to 
* [From tbe same Leetare.] 



OF THE ELDER BACON. 123 

the agency of evil spirits ; and a very short time after 
he had written a book to prove the non-existence of 
magic, he was himself persecuted as an enchanter ; and 
he was imprisoned in 1278, by the command of the 
Principal of the Franciscans, for having brought the 
order to which he belonged into disrepute, by pretend- 
ing to natural wisdom, and by exercising unholy and 
supernatural powers. Roger Bacon appears to have 
made use of the philosophical and experimental method 
of the Saracens, without following any of the absurdities 
of their doctrines. He had seen admirable changes 
produced on bodies, and he knew not the limits of the 
operations of nature. By him, the production of gold, 
and the transmutation of metals, were considered only 
as objects worthy of investigation ; but he never affirmed 
confidently concerning them. He had made many im* 
portant discoveries, — ^particularly that of an explosive 
ccHUpound, sinular to gunpowder: and yet he seldom 
suffisred his imagination to cloud his reason ; and he was 
no enthusiast in regard to the merit of his inventions. 
He possessed the modest and dignified feeling of science. 
But most of the alchemists, who flourished in the next 
century, were of a veiy different complexion. They 
formed themselves into a fraternity ; they professed to 
be in possession of great and important secrets ; they 
connected a peculiar mysticism with their philosophical 
doctrines ; they attached to alchemy a language similar 
to that which had been employed in the platonic philo«' 
sophy ; and they pretended, not only to a knowledge of 
the materials of the globe, and tlie changes of things, 
but likewise to an acquaintance with the elements and 
the spiritual powers by which they supposed they were 
governed. 

q2 



124 ] SKETCH OF THE CHARACTER 



[OF NEWTON .*] 

There are, undoubtedly, in science, fortunate combi- 
nations ; there are happy times, in which new inventions 
bestow new powers, and in which men are, as it were^ 
compelled to follow an easy path to glory ; but, for all 
this occasional interference of accident, labour — steady 
and uninterrupted labour — and the virtue of continued 
attention, are the true sources of noble and happy dis- 
coveries ; and whoever possesses these enviable habits 
of mind, has the chief and the most certain elements of 
success. In the study of nature, there can be no ex- 
ertion thrown away ; for the general laws belonging to 
it, are no less simple and grand, than the economy which 
they govern is complicated and minute; and, when 
observation is carried as far as the senses can reach, it 
is still capable of being rendered more accurate, by 
means of the different apparatuses of instruments, which 
are constantly becoming more perfect ; so that the phi- 
losopher who, having ascertained great truths in a par- 
ticular department of science, should pretend to fix 
them as limits, would act as ridiculously as that Danish 
king, who commanded the ocean to stay its waves. 
When Newton was asked by Dr. Pemberton, to what 
he owed his great discoveries, he said to his habitual 
and patient attention; and the same great man, in a 
conversation in his later years, upon the progress of 
discovery, having asked, ^what was doing at Cam- 
bridge,' and being answered by Dr. Barrow, that ' there 
was nothing doing,' that he had ^occupied all the 
ground,' jocosely said, ^ Beat the bushes, and there is 
still plenty of game to be raised.' 
* [These reflectiona on Newton occur as a fragment in a note-book.] 



OF NEWTON. 126 

Original profondity of genius, talents for abstracted 
research, and vigorous constitution of mind, combined 
^th sagacity and acuteness, are undoubtedly associated 
with the powers by which lofty truths are attained ; and 
they belonged, in the highest degree, to the author of 
the Principia, and the Optics ; but these alone, though 
essential to the development of his abilities, would have 
accomplished nothing, without the faculty of continued 
exertion, which induced him to pass successive nights 
and days in contemplation, inattentive to the wants of 
the body ; which enabled him to attain that sublime 
state of intellect, in which all sensible objects are ex- 
cluded, and in which the mind was nourished by its 
own thoughts concerning the laws of the heavens and 
the earth made the subjects of active meditation. 

By a singular concurrence of circumstances it was 
reserved for the same great genius who developed the 
laws of the planetary system, and who unfolded the 
harmonious movements of the great masses of matter 
in the universe, — it was reserved for Newton to lay the 
foundation of the first theory of chemical action, and 
to solve the diversified phenomena of corpuscular 
changes, by a great and universal principle, similar to 
that wliich he had before applied to the phenomena of 
the heavenly bodies. Newton, towards the close of his 
fife, was made Master of the Mint; and that this office 
was once bestowed upon a man of science, was a great 
and glorious circumstance for the progress of chemistry. 
Newton performed the duties of Master of the Mint, 
and made a number of experiments upon metallic solu- 
tions and alloys. He discovered several new alloys, 
particularly that of a mixture which fuses at the heat 
of boiling water and which is composed of lead, tin, 
and bismuth. In reasoning upon die phenomena of 



126 SKETCH OF THE CHARACTER 

the difisolvent powers of acidly his sagacious mind at 
once perceived the extension of an order which {»«<- 
vailed with respect to the great arrangements of matter. 
Sugar dissolves in water, alkalies unite with acid% 
metals dissolve in acids. " Is not tbis,^ said Newton, 
<< on account of an attraction between their particles ? 
Copper, dissolved in aquafortis, is thrown down bj 
iron. Is not this because the particles of the iron have 
a stronger attraction for the particles of the acid than 
those of copper? and do not different bodies attract 
each other with di£Eerent degrees of force ? " ''^ 

A principle, at once so beautiful and simple, and 
enforced by the authority of such a master, was im« 
mediately adopted* Greoffiroy, the most able chemist 
in the Academy of Science, two years after Newton 
had published a complete development of his chemi- 
cal opinions, attempted to make a table of chemical 
attractions, and to show, by numerical expressions, the 
powers which bodies have of separating each other from 
solvents. His manner of doing this waa, however, fiur 
from being generous. He changed the name of attract 
Hon to that of affinity^ and made no mention whatever 
of the original inventor in his paper. Though the 
principle was referred to Newton by Senac, who pub- 
lished an elementary book on chemistry, in French, in 
1723; yet still the authority of Geo£Eroy, and his sue* 
cessors in the academy, who produced several popular 
elementary works on chemistry, influenced, in a hi^ier 
degree, the public opinion, and for a long time the 
erroneous and vague term, affinity, was substituted &r 
a word which implied the simple expression of a fact. 

The greatness of the reputation of Newton, at this 

* Newton'8 Works, 4to. vol. iv. p. 242. [This and the two following 
paragraphs, are from a Chemical Lecture of 1810.] 



OF CAVEBTDISH. 127 

period, rendered lus own countiymen almost indifferent 
to his claims in chemical philosophy. In the abun- 
dm)ce of the rich stores which he afforded to science, 
such a small contribution was hardly missed. The con- 
troversy concerning the invention of fluxions was of a 
higher character; and the lustre of his mathematical 
philosophy, in some measure, threw his chemical dis* 
coveries into shade. But justice is the first principle 
of philosophical history. It is not with the vain idea 
of adding to the reputation of Newton, that I make 
these statements; not from the unworthy motive of 
expressing feelings of nationality ; but for the sake of 
following truth, and of attributing glory where glory is 
jusdy due. 



[OF MB. CAVENDISH.*] 

Of all the philosophers of the present age, Mr. Caven* 
dish was the one who combined, in the highest degree, 
a depth and extent of mathematical knowledge with 
delicacy and precision in the methods of experimental 
research. It may be said of him, what can, perhaps, 
hardly be said of any other person, that whatever he 
has done has been perfect at the moment of its pro- 
duction. His processes were all of a finished nature. 
Executed by the hand of a master, they required no 
correction ;'and though many of them were performed 
in the very infancy of chemical philosophy, yet their 
accuracy and their beauty have remained amidst the 

* [From a Chemical Lecture delivered in 1810, shortlj after Mr. 
Cavendish's death ; it was in considering the progress of chemical dis- 
covery and the contributions made to it by this eminent philosopher, 
that the anthor digressed into the character of the man.] 



128 SKETCH OF THE CHABACTER 

progress of discovery, and their merits have been illus- 
trated by discussion, and exalted by time. 

In general, the most common motives which induce 
men to study are, the love of distinction, of glory, or 
the desire of power; and we have no right to ob* 
ject to motives of this kind; but it ought to be 
mentioned, in estimating the character of Mr. Caven* 
dish, that his grand stimulus to exertion was evidently 
the love of truth and of knowledge. Unambitious, 
unassuming, it was with difficulty that he was persuaded 
to bring forward his important discoveries. He disliked 
notoriety, and he was, as it were, fearful of the voice of 
fame. His labours are recorded with the greatest 
dignity and simplicity, and in the -fewest possible words, 
without parade or apology ; and it seemed as if in pub* 
lication he was performing, not what was a duty to him- 
self, but what was a duty to the public His life was 
devoted to science, and his social hours were passed 
amongst a few fiiends, principally members of the 
Royal Society. He was reserved to strangers; but, 
when he was familiar, his conversation was lively, and 
fiiU of varied information. Upon all subjects of science 
he was luminous and profound ; and in discussion won- 
derfully acute. Even to the very last week of his life, 
when he was nearly seventy-nine he retained his activity 
of body, and all his energy and sagacity of intellect. 
He was warmly interested in all new subjects of science; 
and several times in the course of the last year witnessed, 
or assisted in, some experiments which were carried on 
in this theatre, or in the laboratory below. 

Since the death of Newton, if I may be permitted to 
give an opinion, England has sustained no scientific 
loss so great as that of Cavendish. Like his great 
predecessor, he died full of years and of glory. His 



OP CAVENDISH. 129 

name will be an object of more veneration in future 
ages than at the present moment Though it was un- 
known in the busy scenes of Kfe, or in the popular dis- 
cussions of the day, it will remain illustrious in the 
annals of science, which are as imperishable as that 
nature to which they belong; and it will be an im- 
mortal honour to his house, to his age, and to his 
country.* 

[The author in his Introduction to the Elements of 
Chemical PhOosophy, vol. iv. p. 30, alludes to Caven- 
dish's two grand discoveries, — the composition of water 
and of nitric acid, — in a manner clearly indicating his 
conviction that Mr. Cavendish's claims to both were 
unquestionable. This I mention, with reference to the 
attempt which has been recently made by M. Arago, 
supported by Lord Brougham, to appropriate the merit 
due for one of these discoveries, that of the composi- 
tion of water, solely to Mr. Watt. That the honour of 
the discovery was shared between these two illustrious 
men, has hitherto been commonly received ; and that 
more is due to the latter, is neither proved, it appears to 
me, by M. Arago in his Eloge, nor by Lord Brougham 
in the supplementary article. The author's opinion on 
this important point, (important as it surely is in the 
history of science,) can hardly be considered but of 
great weight Well acquainted with Mr. Cavendish 
and Mr. Watt, intimately acquainted with his son, Mr. 
Gregory Watt, in habits of daily intercourse with men 
of science, the contemporaries of the two former, as 
Sir Joseph Banks, Sir Charles Blagden, Dr. George 
Pearson and others, — he had the best opportunities not 
only of learning the current opinion on the subject, 
but also of ascertaining the truth. Li one of his early 
* [From the same Lecture.] 

o 5 



130 OX THE CLAIH9 OF M|t. CAVENDISH TO THE 

lectures, without date, but which flrom some remarks 
contained in it, may b^ inferred to have been written 
about 1806, there is a brief historical sketch of the 
discovery in question, which though evidently haatily 
written, may be deserving of insertion here, as a dear 
statement on the matter at issue.] 

No natural substance [the author remarks] presents a 
more important series of investigations to the chemist 
and philosopher than water; the object so constandy pre- 
sented to us; and the usea and effects of which are so 
familiar. 

The appearances of this fluid are simple and uni* 
form. And, when we consider the immense quantities 
in which it is found, and its almost universal agencies, 
it is easy to conceive how those ideas were formed, ac- 
cording to which it was so long supposed to be the 
most active and the most perfect of the elements. 

^« Water is the best," says the great lyric poet of the 
Greeks ; and by this he evidently meant to express the 
doctrine of Thales, ^' that it was the great and active 
principle of Nature," an opinion which has been often 
supported ; and which has appeared in some of the 
earlier theories of modem times* 

Our knowledge of the true nature and effects of 
water is wholly derived from the discoveries of Pneu- 
matic Chemistry, Till the year 1780, it was almost 
universally believed to be a simple body; and in 
tracing the history of opinion with regard to it before 
that period, we find only one conjecture which bears 
any relation to the truth ; and that was formed by the 
unparalleled sagacity of Newton, who ventured to sup- 
pose from the high refractive powers of water that 
it must contain inflammable matter. 

After the important properties of hydrogen gas had 



DISCOVERY OP THE COMPOSITION OF WATER, 131 

been discovered bj philosophers, experiments were 
continuallj made upon its combustion, both for the pur- 
pose of amusement and with the view of detecting the 
cause of the phenomena. 

Various theories were invented : Scheele, who had 
performed the detonation of hydrogen and oxygen 
in open vessels only, and who found in these vessels 
after the process common air, supposed that the two 
gases had combined, and that their product was heaty — 
a bold conjecture, yet stamped by the genius of the mauy 
and conformable to the observation which he had 
made ; an observation imperfect from the want of proper 
^paratus. 

Macquer as early as 1774 had observed that moisture 
was formed in the combustion of inflammable air; 
but this moisture was generally believed to be water 
which had been dissolved by the gas ; and it was not 
till the summer of 1781, that the fact was perfectly un- 
derstood. At this time Mr. Cavendbh, in a process 
conceived with his usual sagacity, and executed with 
his usual precision, showed that when common air and 
hydrogen were exploded together in the proportion of 
2\ to 1, the product was pure water, which exactly cor* 
responded in weight to the gases consumed. And Mr. 
Watt, reasoning on this experiment, formed the conclu- 
sion ** That water consisted of pure and inflammable air 
deprived of the greatest portion of their latent heat." 

The discovery was generally admitted : and con- 
firmed by the investigations of Lavoisier and the 
French chemists, it became the principal basis of that 
generalization which has been since called the anti* 
phlogistic theory, and formed the most impressive and 
convincing fact of the doctrine. 

Many of the experiments on the decomposition and 



132 ON THE CLAIMS OF MR. CAVENDISH TO THE 

Composition of water have been several times made in 
this theatre : and I am well aware that the appearances 
must be fiuniliar to a part of my audience ; but I may 
reasonably conjecture diat many are present who have 
never witnessed them. In an elementary course on the 
operations of the chemistry of the gases it would be 
improper to omit so important and essential a series. 
I have witnessed them very often, I have performed 
them many times, and yet Uiey seem always to afford 
me some new elucidations, some new subjects for in- 
quiry, or some new object for speculation. 

[In the opinio^ expressed by the author, there is no 
detraction; the fact of the discovery implying the 
inference is assigned to Mr. Cavendish ; ^- the happy 
inference, independently made requiring to be con- 
firmed to constitute a discovery, is assigned to Mr. 
Watt : — this was the decision of contemporaries, 
and with this Mr. Watt appears to have been con- 
tented. The contrary conclusion, it appears to me, 
cannot be sustained without involving consequences of 
the highest improbability, — implicating the character of 
Mr. Cavendish for truth, honour, and honesty, — im- 
plying a conspiracy against Mr. Watt, on the part of the 
Secretaries, President, and Council of the Royal 
Society, — and a want of courage and determination on 
the part of Mr. Watt and his friends, Dr. Priestley and 
Mr. De Luc, to come forward and vindicate his just 
claims. A dispassionate perusal of the writings bearing 
on the subject, and on collateral subjects of inquiry 
during that period of active research, especially the 
papers of Dr. Priestley, in the Philosophical Transactions 
for 1783 and 1785, — of Mr. Kirwan in the same 
Transactions for the intermediate year, and of Mr. 
Cavendish and of Mr. Watt in the same volume, — it 



DI8C0VBKY OP THE COMPOSITION OF WATER. 133 

appears to me, can hardly fail to lead to that conclu- 
sion which is alike honourable to Mr. Watt and to 
Mr. Cavendish^ and which is free from all the diffi- 
culties and painfid consequences connected with the 
contrary. 

According to my apprehension of the statements, the 
simple facts bearing on the question are the following. 
Dr. Priestley, in his paper on *' the seeming conversion 
of water into air," bearing date Birmingham, April 21, 
1783, distinctly mentions ** an experiment of Mr. 
Cavendish concerning the re-conversion of air into 
water by decomposing it in conjunction with inflam- 
mable air;" a result which he confirmed by repetition. 

This result, Mr. Watt states, was the basis of his 
hypothesis respecting the nature of water, and his first 
letter on the subject was written in the same month as 
Dr. Priestley's paper before alluded to ; it was dated 
April 26, 1783. From a passage in Dr. Priestley's paper 
and in Mr. Watt's first letter, it may be inferred, that 
this his hypothetical conclusion was formed just before 
that letter was written ; he mentions in it, the abandon- 
ing of an opinion that he had entertained for many 
years, " that air was a modification of water ; " that by 
a great heat water might be converted into air. 

Now, what is Mr. Cavendish's statement relative to 
the discovery? Afrer describing his experiments in 
proof of the production of water by burning hydrogen 
in close vessels with common air and oxygen gas, he 
remarks: — "All the foregoing experiments, on the 
explosion of inflammable air with common and dephlo- 
gisticated air, except those which relate to the cause of 
the acid found in the water, were made in the summer 
of the year 1781, and were mentioned by me to Dr. 
Priestley, who in consequence made some experiments 



134 ON THB CLAIMS OF MB. CAVENDISH TO THB 

of the same kind, as he relates in a paper printed in the 
preceding volume of the TnxMactunu. During the last 
summer also, a friend of mine gave some account of 
them to M. Lavoisier, as well as of the conclusioiiB 
drawn from them, that dephlogisticated air is only water 
deprived of phlogiston ; but at that time so far was M. 
Lavoisier from thinking any such opinion warranted, 
that till he was prevailed upon to repeat the experi- 
ment himself, he found some difficulty in believing that 
nearly the whole of the two airs should be converted 
into water. It is remarkable that neither of these gen- 
tlemen found any acid in the water produced by the 
combustion ; which might proceed from the latter having 
burnt the two airs in a different manner from what I 
did ; and from the fcnrmer having used a different kind 
of inflammable air, namely that from charcoal, and per- 
hKp& having used a greater proportion of it." 

This statement must be received either as correct, or 
the contraiy. If the former, it is so precise in particu- 
Jars, that there must be an end to all question relative 
to Mr. Cavendish being the original discoverer of the 
composition of water. If the latter, his conduct on the 
occasion must be pronounced to be dishonest and dis- 
honourable, totally incompatible with all that is known 
of his character; and the same sentence must be passed 
on that of his friend, to whom he alludes, who was Sir 
Charles Blagden. 

Lord Brougham, in the examination of evidence on 
the subject, seems to connect suspicion with the cutv 
cumstance, which he has ascertained, that the paragraph 
above quoted was an addition to Mr. Cavendish's MS. 
paper, inserted, he presumes, with his consent, and as he 
supposes, by the Secretary of the Society, Sir Charles 
Blagden. Granted it were so; may it not, under the 



DISCOVBBY OF TH£ COMPOSITION OF WATSR. 135 

circumstances of the case, be considered a confirmation 
of the accuracy of the statements it contains. 

Taking for granted the honour and yeracity of Mr. 
Cavendish, these circumstances appear to have been the 
following. 

In consequence of an experiment of Mr. Warltire, 
in which a production of moisture appeared on ex* 
ploding together common air and hydrogen gas, referred 
to by Mr, Cavendishi and the result of which was ex* 
plained by the former, in the same manner as the simi- 
lar result before obtained and similarly explained by 
Macquer, Mr* Cavendish, in 1781, made the experi- 
ments showing that water is the true product of the 
combustion of hydrogen and oxygen, and drew the 
inference, that water is composed of hydrogen and 
oxygen. 

He makes Dr. Priestley acquainted with his results, 
as Dr. Priestley mentions. Dr. Priestley repeats the 
experiment, and obtains similar results. He commu- 
nicates them to his fiiend Mr. Watt ; Mr. Watt seems 
immediately to have seen their importance and bearing; 
and reasoning on them, to have given up his former 
opinion long entertained that water is convertible into 
air by great exaltation of temperature, and to have 
come to the conclusion ^^ that water is composed of 
dephlogisticated air and phlogiston, deprived of part of 
their latent or elementary heat ; that dephlogisticated 
or pure air is composed of water deprived of its phlo* 
giston and united to elementary heat and light; and 
that the latter are contained in it in a latent state, so as 
not to be sensible to the thermometer or to the eye ; 
and if light be only a modification of heat, or a circum- 
stance attending it, or a component part of the inflam- 
mable air, then pure or dephlogisticated air is composed 



136 ON THE CLAIMS OF MR. CAVBNDISH TO THE 

of water deprived of its phlogiston and united to ele- 
mentary heat.** 

These inferences were expressed in Mr. Watt's first 
letter, that to Dr. Priestley of the 27th April, 1783, 
which the latter, after showing it to several members of 
the Royal Society, placed in the hands of the President 
to be read at a meeting of the Society, but which was 
not read in consequence of the particular request of 
Mr. Watt to that efiect, doubts as to the probability 
of his inferences having been raised in his mind, it 
would appear, by some new experiments of Dr. Priestley. 

Whilst his paper is thus standing over, Mr. Caven- 
dish brings forward his ^^ experiments on air," those de- 
monstrating the composition of water. This paper was 
read before the Royal Society January 15, 1784. Mr. 
Watt, it appears, had been previously ui^d, by his friend 
Mr. De Luc, to bring forward his hypothesis ; and this 
he accordingly does in a letter addressed to this gentle- 
man, dated Birmingham, November 26, 1783, prefiusing 
it with the remark, ^' I feel much reluctance to lay my 
thoughts on these subjects before the public in their 
present undigested state, and without having been able 
to bring them to the test of such experiments as would 
confirm or refiite them." This letter, in which was 
incorporated portions of his first letter, was read before 
the Royal Society on the 29th April, 1784, three months 
after Mr. Cavendish's, and before Mr. Cavendish's was 
printed. 

Now, on the former presumption of Mr. Cavendish's 
truthfulness and honour, having made the discovery 
described in his paper, was it not perfectly natural that 
he should wish, and that his fiiend should wish, to 
insert a paragraph, stating what he had done in the 
inquiry in point of time, thereby establishing his right 



BI8COVBBY OF THB COMPOSITION OF WATBB. 137 

to originality of discovery, both as to matter of fact 
and of inference, that is, that he saw water result from 
the burning of hydrogen gas, and inferred that water is 
composed of this gas and of oxygen ; nor was it con- 
trary to the usages of the Society to allow of the inter- 
polation : the dates of the respective papers of Mr. 
Cavendish and of Mr. Watt were sufficient proof that 
the passage in question was an addition. 

And, the manner in which Mr. Cavendish speaks of 
Mr. Watt's views, in another passage which was added, 
appears to me, on the same presumption of integrity on 
the part of the former, strongly confirmatory of the 
common opinion, that their conclusions were formed 
independent of each other. The passage is the follow- 
ing, and it is an excellent example of Mr. Cavendish's 
perspicuity and logical precision. 

<< From what has been said (having detailed his ex- 
periments), there seems the utmost reason to think, that 
dephlc^isttcated air is only water deprived of its phlo- 
giston, and that inflammable air, as was before said, is 
either phlc^sticated water, or else pure phlogiston; 
but, in all probability, the former. 

** As Mr. Watt, in a paper lately read before this So- 
ciety, supposes water to consist of dephlogisticated air 
and phlc^ton, deprived of part of their latent heat, 
whereas I take no notice of the latter circumstance, it 
may be proper to mention, in a few words, the reason 
of this apparent difference between us. If there be any 
such thing as elementary heat, it must be allowed, that 
what Mr. Watt says is true ; but, by the same rule, we 
ought to say, that the diluted mineral acids consist of 
the concentrated acids united to water, or deprived of 
part of their latent heat ; that solution of sal ammoniac, 
and most other neutral salts, consist of the salt united 



138 OX THE CLAIU8 OF MR. CAVENDISH TO THE 

to water, and elementary heat ; and a similar language 
ought to be used in speaking of almost all chemical 
combinations, as there are very few which are not at- 
tended with some increase or diminution of heat Now 
I have chosen to avoid this form of speaking, both be- 
cause I think it more likely that there is no such thing 
as elementary heat, and because saying so, in this in- 
stance, without using similar expressions, in speaking of 
other chemical unions, would be improper, and would 
lead to false ideas ; and it may even admit of doubt, 
whether the doing it in general would not cause more 
trouble and perplexity than it is worth." 

M. Arago, in advocating the cause of Mr. Watt, lays 
some stress on the manner in which Mr. Watt's hypo- 
thesis was received by the Council of the Royal Society, 
" Son etrangete fait meme douter de la v6rite des ex- 
periences de Priestley, On va jusqu'i en rire^ dit De 
Luc, comme de VexpUcaticn de la dent JCorJ* 

Granted, — ^but this cannot apply to Mr. Cavendish, 
as the experiment of Priestley was merely a repetition of 
Mr. Cavendish's. Considering the peculiar shyness oif 
this extraordinary man, and his great reserve, it is not 
surprising that the Council of the Royal Society should 
be as ignorant of the conclusion he drew from his ex- 
periment on the combustion of hydrogen, in which 
water appeared, as of the experiment itsel£* His shy- 
ness and reserve, I have always understood were beyond 
all description. They are particularly noticed, in a 

* [Mr. Cavendish at this time was not on the Council of the Royal 
Society ; he was first elected on the Council In 1786. 

From the Minutes of the Council it appears that Mr. Watt's letter was 
i«ad before it came before the Committee of Papers, namely^ on the 6th 
May, 1784, at one of the ordinary meetings of the Society, and was 
brought before the Committee on the 20th of the same month, when it 
was ordered to be printed together with a postscript.] 



DISCOVBRT OF THE COXPOSITIOK OF WATER. 139 

aketdi of him by the author, one of the many which 
he amused himself in writing from recollection during 
Us last illness, as has been abready mentioned. It may 
be deserving of a place here ; especially as it is per- 
fectly in accordance with his character by the same 
hand, already given, though drawn in a different attitude, 
and with a different pencil, and in accordance with the 
idea, that he was a man of integrity, incapable of stoop- 
ing to any meanness.] 

Cavendish was a great man, with extraordinary singu* 
larities. His voice was squeaking, his manner nervous, 
he was afraid of strangers, and seemed, when embar* 
rassed, even to articulate with difficulty. He wore the 
costume of our grandfathers: was enormously rich, but 
made no use of his wealth. He gave me once some bits 
of platinum, for my experiments, and came to see my 
results on the decomposition of the alkalies, and seemed 
to take an interest in them ; but he encouraged no in* 
timacy with any one. He left 15,000^ to Sir Charies 
Blagden by will, probably because they had once been 
great friends, and had ceased to be so. It is said that 
Sir Charles Blagden had early pecuniary obligations to 
Cavendish. He (Cavendish) lived, latterly, the life of 
a solitary, came to the Club dinner, and to the Royal 
Society, but received nobody at his own house. He 
was acute, sagacious, and profound, and, I think, the 
most accomplished British philosopher of his time. He 
was about eighty when he died.* 

* [He died, I haye been aasured, in the most tranquil manner. A per- 
fon employed by him about his apparatus told me that the last thing 
Mr. Cavendish called for, waa a glasa of water, and then he desired to be 
alone : his attendant being uneasy respecting his state, retired to a dis- 
tant part of the room. Mr. Cavendish drank some of the water, turned on 
his side, and shortly expired, without uttering a word or even a sound, 
much in the manner of his illostrloas contemporary Dr. Black, who died 



140 SPEECH IN EULOGY 

[A few pages back the aathor^s intimacy with Mr. 
Gregory Watt has been alluded to ; in the first volume, 
the circumstances under which it was formed have been 
described; in a geological lecture delivered in 1811, in 
referring to Mr. Gregory Watt's experiments on the 
fusion and slow cooling of basalt, and his paper on the 
subject, ^^ abounding in acute observations and sagar 
cious inferences," which was published in the Philoso- 
phical Transactions; he adds,] It was the first and 
only geological production of a mind full of talent and 
enthusiasm for scientific pursuits — of a mind which 
promised much for the philosophy of this subject ; but 
death cut off this bloom of promise and hope for the 
scientific world at the moment when it was brightest. 
No person attached to truth can read his paper without 
a feeling of regret, and I hope I may be excused for 
the strong expression of this regret, for whilst I ad- 
mired him as a philsopher, I loved him as a man. He 
was the earliest and one of the dearest of my scientific 
firiends. 

[The author's respect for the illustrious father, was 
expressed on very many occasions, but on no one more 
powerfully than at that memorable meeting which was 
held at Freemason's Hall, in London, on the 18th June, 
1824, for erecting a monument to Mr. Watt, at which 
Lord Liverpool, then Prime Minister presided, and at 
which some of the most distinguished men in the coun- 
try, came forward, and in speeches of glowing elo- 
quence, which it is difficult now to read without emotion, 
bore testimony to the merits of the man and of the 
philosopher^ and of his extraordinary claims to the 

as if he had fallen asleep, with an nnspilled basin of milk on his knees, 
sitting in his chair. Vide the interesting account of the event in Dr. 
Bobhison's Pre&ce to Dr. Black's Lectures.] 



OF ME. WATT. 141 

gratitude of his country^ and of the world. It was on 
this occasion^ feelingly designated by Sir Robert Peel^ 
as an "awfiil and affecting occasion," and happily 
called by Sir James Mackintosh " a public solemnity in 
honour of the useful arts ;" and which Mr. Wilberforce, 
in his best manner of philosophical benevolence con- 
trasting with other meetings of pohtical and party 
debate and contention to which they were accustomed, 
characterized as one, where ^'we seem to rise into a 
higher region of light and truth, of genius and of 
science, where none of those passions darken and none 
of those baser emotions discompose the atmosphere, 
that are generated in the scufflings of the vale below," — 
it was on this occasion, which it is reaUy delightful to 
dwell on, that the author in moving the first resolution, 
thus addressed the meeting.] 

I ought to apologize for rising so immediately to 
address this meeting, but as the distinguished person 
whose memory we have met together to honour, owes 
his claims to the gratitude of society to his scientific 
labours, and as he was one of the most illustrious Fel- 
lows of that Institution for the promotion of natural 
knowledge over which I have the honour to preside, I 
consider it as a duty incumbent on me to endeavour to 
set forth his peculiar and exalted merits, which live in 
the recollection of his contemporaries, and will transmit 
his name with immortal glory to posterity. Those who 
consider James Watt only as a great practical mechanic, 
form a very erroneous idea of his character, — ^he was 
equally distinguished as a natural philosopher and a 
chemist, and his inventions demonstrate his profound 
knowledge of those sciences, and that peculiar charac- 
teristic of genius, the union of them for practical appli- 
cation. The steam engine, before his time, was a rude 



142 SPEECH 15 EULOGY 

machine^ the result of simple experiments on the cotn- 
pression of the atmosphere^ and the condensation of 
steam. Mr. Watfs improvements were not produced 
bj accidental circnmstances^ or by a single ingenious 
thought, they were founded on delicate and refined ex- 
periments connected with the discoveries of Dr. Black. 
He had to investigate the cause of the cold produced 
by evaporation, of the heat occasioned by the condens- 
ation of steam ; to determine the source of the air ap- 
pearing when water was acted upon by an exhausting 
power ; the ratio of the voltime of steam to its genera- 
ting water, and the law by which the elasticity of steam 
increased with the temperature; labour, time, numerous 
and difficult experiments were required for the ultimate 
result ; and when his principle was obtained, the appli- 
cation of it to produce the movement of machinery 
demanded a new species of intellectual and experimen- 
tal labour. He engaged in this with all the ardour 
which success inspires, and was obliged to bring all the 
mechanical powers into play, and all the resources of 
his own fertile mind into exertion ; he had to convert 
rectilinear into rotatory motion, and to invent parallel 
motion. After years of intense labour he obtained 
what he wished for ; and at last, by the regulating cen- 
trifugal force of the ffovemor, placed the machine 
entirely under the power of the mechanic, and gave 
perfection to a series of combinations unrivalled for 
the genius and sagacity displayed in their invention, 
and tor the new power they have given to civilized 
man. 

Upon the nature of this power I can hardly venture to 
speak ; so extensive and magnificent a subject demands 
a more accomplished and able orator. What is written 
on the moniHDent of another illustrious and kindred 



OF MB. WATT. 143 

philosopher* in rehition to one great iroA, and a sinj^e 
spot will apply to Watt in almost evexy part of the 
ampire: — 

" Si momunentiim reqoiiiay drciimspice." 

And where can we cast our eyes, without seeing 
zesnlts dependent upon, or connected with his inven- 
taoas ? Look round on the metropolis ; our towns> even 
oor villages ; our dock-yards, and our manufactories ; 
examine the subterraneous cavities below the surface, 
and the works above ; contemplate our rivers and our 
canals, and the seas which surround our shores^ and 
every where will be found records of the eternal bene- 
fits conferred on us by this great man. Our mines are 
drained^ their products collected, the materials for our 
bridges raised; the piles for their foundation sunk by the 
same power; machinery of every kind, which formerly 
required an immensity of human labour, is now easily 
moved by steam; and a force equal to that of five 
hundred men is commanded by an in&nt, whose single 
hand governs the grandest operations. The most labo- 
rious works, such as the sawing of stones and wood, 
and raising of water are efiected by the same means 
which produce the most minute ornamental and elegant 
fiufms. The anchor is forged, the die is struck, the 
metal polished, the toy modelled, by this stupendous 
and universally applicable power : and the siune giant 
arms twist the cable rope, the protector of the largest 
dnp of the line, and ^in the gossamer-like threads 

* [TfaeinBcriptioii abore alluded to, to that in St. Panrs on the momi* 
mtnt of Sir Christopher Wien ; it is as follows : — 

aUBTUS ' CONDITUB ' HUIUS * BCCLESIiB * £T ' UBBIS 

CONDITOR • CHRI8TOPHORUS ' WRBN ' QUI ' TIXIT 

ANK08 • ULTRA ' NONAOINTA * WOK ' STBI * 8BD 

BOIf O-rUBLICO * LBOTOR * »Z * MONUMBKTITM * BBQUIMB 

CIBOUM»PIOB.] 



l44 6PBECH IN BULOOY 

which are to ornament female beauty. Not only have 
new arts and new resources been provided for civilized 
man by those grand results, but even the elements have 
to a certain extent been subdued and made subservient 
to his uses ; and by a kind of philosopical magic, the 
ship moves rapidly on the calm ocean, makes way 
against the most powerful stream, and secures her 
course, and reaches her destination even though op- 
posed by tide and storm. 

The Archimedes of the ancient world by his me- 
chanical inventions, arrested the course of the Romans, 
and stayed for a time the downfall of his country. How 
much more has our modem Archimedes done? He 
has permanently elevated the strength and wealth of 
this great empire, and during the last long war, his in- 
ventions and their application were amongst the great 
means which enabled Britain to display power and re- 
sources so infinitely above what might have been ex- 
pected from the numerical strength of her population. 
Archimedes valued principally abstract science : James 
Watt, on the contrary, brought every principle to some 
practical use ; and as it were made science descend from 
heaven to earth. The great inventions of the Syracu- 
san died with him, those of our philosopher live, 
and their utility and importance are daily more felt; 
they are among the grand results which placed civilized 
above savage man, — which secure the triumph of intel- 
lect, and exalt genius and moral force over mere 
brutal strength, courage, and numbers. The memory of 
James Watt will live as long as civilised society exists; 
but it surely becomes us who have been improved by 
his labours, — who have wondered at his tfdents and 
respected his virtues, to offer some signal testimony of 
our admiration of this great man. This, indeed, can- 



OF MR. WATT. 145 

not exalt his glory, but it may teach those who come 
after us that we are not deficient in gratitude to so 
great and signal a bene&ctor. I5 therefore, my lord, 
beg leave to move, '^ That the late James Watt, by the 
profound science and original genius displayed in his 
admirable inventions, has, more than any other man of 
this age, exemplified the practical utility of knowledge, 
enlarged the power of man over the external world, and 
both multiplied and difiused the conveniences and en- 
joyments of human life. 

[Neither in this speech, nor in any of the others 
delivered at the same meeting, is there any allusion 
made to Mr. Watt as the discoverer of the chemical 
composition of water ; by every speaker the subject is 
entirely passed over, which surely on such an occasion, 
is not what might have been expected, if the merit of 
the discovery was truly his and not Mr. Cavendish's, 
and if it had been supposed that justice had not been 
done to the former.] 



VOL. VII, 



146 



[In the First volume, page 99, aUosion has been made 
to the manner in ^hich the author spent his time, when 
not engaged in research in the laboratory, especially 
during the summer vacations, and how in his excursions 
into the country, he combined with recreation for the 
sake of health, the study of geology and agriculture. 
As an example of his manner of proceeding on these 
occasions, it may not be amiss to insert a portion of a 
Journal of a tour which he made in Ireland, in the 
early summer of 1806, showing, as it does, the objects 
for which he travelled, and the systematic mnnner in 
which he observed ; and perhaps for another reason, as 
it conveys the impression made on his mind by the 
country and people in districts in many respects pe- 
culiar and out of the track of ordinary tourists. The 
reader should keep in recollection, that the journal 
was intended solely for his own use ; that it was never 
copied by the author, or even looked over for correc- 
tion ; and in brief, that it is composed merely of rough 
notes, some of which, in consequence of the haste in 
which they were written, it is difficult to decipher. 
The journal is a fragment, and commences at Lime- 
rick : — ] 

Limerick, June 27. 

1. The journey from Rathkeal to Limerick, with- 
out many objects of interest Small hills, without 



JOURNAL OF A TOUR IK IRBLAND. 147 

wood ; plains cpvered with bog for many miles. Adare 
is the first jdace calculated to airest the attention of the 
travellen Here is wood, fine treesi and some monastic 
bQildii^ beautifiil in their ruins. The architecture, 
where it retains its characteristics, Gothic; the walls 
covered with ivy : a scene denoting ancient splendour, 
whilst the cabins which surround the walls tell a tale of 
existing wretchedness. 

Within four miles of Limerick, a mountain scene is 
developed. The Keeper chain to the east, the Clare 
bills to the north; their forms smooth and generally 
rounded, and the most lengthened inclination to the 
west. 

Limerick, — A large well-built city. The Shannon, 
a fine river; but, though affected by the tide, certainly 
inferior in size (perhaps even in the quantity of water it 
sends down) to the Thames and the Severn, at equal 
distances firom the sea. 

Marks of improvement — Good buildings rising ; a 
handsome race of people, and more pretty young women 
than I have seen since our departure firom London ; a 
fine fall of the Shannon, when the tide is down; and a 
river about a mile above it, where salmon are caught in 
abundance. Limerick might be imagined an English 
town by those who had no dealing with the keepers of 
the inns and of livery stables. No beautifiil or grand 
sceneiy about this city. The banks of the Shannon 
bare, or but little wooded; and no remarkable cha* 
racter in the. river, if the extreme clearness and purity 
of the water be excepted. From Limerick to Neiaiagfa, 
a road through a cultivated country. Views from the 
Shannon, and some fine effects fix)m the Keeper moun- 
tcuns. 

2. Geology of Limerick, and the mountains bor- 
h2 



148 JOURNAL OF A TOUR IN IRELAND. 

dering upon it : — Sandstone, schist and sandstone occur 
near Rathkeal, and shell Umestone is abundant, on all 
the road from Killamey to Limerick. Several quarries 
have been opened. The character of the rock is dis* 
tinct; much mechanical deposit and little ciystalline 
matter. The colour dark brown, grey, or black. Coal- 
blend occurs between Killamey and Abbey Feale, 
probably beneath the sandstone slate. The limestone 
inclined very little. The strata numerous and parallel; 
the upper exceedingly broken and decomposed, and the 
dip, where it could be distinctly perceived, to the south. 
The shells more abundant in the upper strata. 

These secondaxy strata probably thrown out of 
their horizontal position at the same time with the 
elder strata. Like the elder strata of Kerry, they are 
often curved. The curvature of the shell limestone 
distinct in the road to Abbey Feale, but not upon so 
great a scale as at Ross Island. 

The limestone about Limerick shell-rock, and pro- 
bably in parallel layers. The surrounding mountains 
afford the same substance, with sandstone and slate and 
pebble-stone ; probably the slate lowest, then the pebble- 
stone, then the limestone. 

The Keeper range of mountains, from the smooth- 
ness of their outline, and from the detached stones, are 
probably of similar constitution ; that worked for the 
lead mines, called Silver Mines, afforded, on examina- 
tion, similar facts. A few detached stones of granite 
and sienite on the side of this mountain. A miner 
told us such occurred in the Keeper; but, as the 
greatest part of this mountain is grit and limestone, I 
suspect he has mistaken pebble-stone for primary rock, 
and that the sienite and granite are from the moun- 
tains of Kildaie or Carlin. Amongst the line of moun- 



JOURNAL OF A TOUR IN IRELAND. 149 

tains to the east of Nenagb, is a mountain most sin- 
gularly indented, called the " Devil's Bite," and tradi- 
tionally said to be a road made for the devil and his 
goats. It is a great limestone rock (i.e. I am told so). 
The appearance is probably owing to a sudden sinking 
of a great portion of a parallel stratum, and the rock, I 
conceive, must be shell-rock. The tact is the more 
singular, as the surrounding mountains are gently 
roanded, but this presents only straight lines. 

3. Land well cultivated for Ireland ; much pasture, 
bat no irrigation ; not much liming ; the soil veiy cal- 
careous ; wheat and barley, but little flax. 

4. The lower classes poorly clad, and nearly as 
miserable as those of Cork. No marks of that enthu- 
siasm of character which sometimes occurs in Ireland. 
Idleness without thought, and the old association of 
ignorance and impudence. Miserable articles of Irish 
manufacture, spoken of by their vendors as superla- 
tive. The Limerick hooks and flies altogether fallen 
off, veiy bad, and very expensive; yet every paltry 
fisherman considers himself as the best fly-tyer ^^in 
Limerick, in Dublin, in all Ireland, ay, and in Eng- 
land too — ay, and in the whole world" — having " the 
best colours, making the neatest hook, and having the 
quickest eye and the naitest hand." 

The shops well furnished with English manufac- 
tures. All comforts, all luximes, all spirit of im- 
provement, all that makes Ireland important and 
respectable, are either of foreign growth or of foreign 
education. The great vice of the people is want 
of perseverance: nothing is finished; they begin 
grandly and magnificently, but complete very little. 
In mining, they build machinery before they have 
discovered a vein; in the fisheries, they erect their 



150 JOURNAL OF A TOUR IN IRELAND. 

cellars before they have purchased nets; and they 
build magnificent stables^ which they intend for thefar 
studs, but ^Aiich they are themselves obliged to in- 
habit. Foresight and prudence are unknown. 

Edgeworth Toh)7u — First aspect of the country 
between Nenagh and Edgeworth Town flat, bare, and 
without any objects of beauty. The course of the 
Shannon is through a flat country ; its banks bare and 
reedy ; its current slow ; sometimes deep and still, and 
confined within shores of one hundred yank, at other 
times expanded into lakes, with islands. No moun- 
tains ; hills so rare, that a woman at Athlone, recom* 
mending us to take fi>ur horses on account of the 
At&, said they were ^terrible bills, very high, as high, 
ay, and higher too, than the house," which was an 
exceedingly low edifice of two stories. The Shannon 
at Portumna is deep, but rapidly spreads out in its 
course into a great loch. At Banagher it is rapid be- 
low the bridge, and at Athlone still more rapid, and 
not more than fifty yards over. The little river 
Inny runs by Ballinachur. Here are hills, but no wood, 
and bog or grass land, with some arable. Flax and 
barley, and a little wheat 

The country about Edgeworth Town flat, but an 
amphitheatre of hills surrounding the plain. None 
of them very high, probably all less than 1000 feet. 
One hill, the hiU of Ardar, we ascended, and saw 
a great extent of ground : the quiet Shannon rolling 
sleepily and slowly through green meadows and brown 
bogs, to the south: to the west, a great range of 
very distant mountains; to the north the hills of 
Westmeath, low and rounded ; to the east, fog, where, 
in a clear day, we might have seen the mountains 
of Wicklow. 



JOURHAL OF A TOUR IIT IRELAND. 161 

2. Limestone, sandstone, and puddingtftone, in yarioos 
associations. 

3. Except the moral and intellectual . paradise of 
eke author of *^ Castle Backrent^'' nothing worthy of 
obeervation. 

4. The eoun^ of Westmeath and that of Long-- 
ford aboand in small lakes, which are surrounded by 
bogs; and in the shores of them, in dry seasons, the 
horns and bones of deer are discovered in great 
abundance. This country, now so bare, was anciently 
an immense forest; and it is an object which might 
employ speculation as worthily as many other objects, 
whether the great change was owing to the slow ope* 
latipns of natuns, decay, or to some great convulsion or 
inundation. 

Donegal, July 17. 

1. Aspect of the country from Edgeworth Town to 
Belturbet, without any mitfked traits of beauty ; some 
lalls to the south possessing a varied outline, but a 
general want of wood; gteen and cultivated fields, 
bogs and heath land. 

From Belturbet to Enniskillen an exceedingly beau- 
tiful country. The Erne appears, at Belturbet, im- 
mediately in the town, a rapid torrent, but becoming 
a lake abote and below. The access to Loch Erne 
is through rounded hills, green with pasture; few 
trees. From the top of the hill, about eight miles 
fiom Belturbet, the lake appears a noble expanse of 
water, with many wooded islands. A green and cul- 
tivated hill, of most graceful form, the principal near 
object, and some blue mountains in the back-ground, 
tabular and smooth ; a view of great extent, soft and 
quiet, without rudeness of form or strong contrast of 
eolouritig, yet impressive from its magnitude, from 



152 JOURNAL OF A TOUR IV IRELAND. 

the variety of land and water, and from the beauty of 
cultivation. A number of lakes of various sizes, few 
exceeding two miles in circumference, border the 
upper part of Loch Erne, and pour their waters 
into the Upper Erne ; but the banks of most of them 
are boggy. There is no rock-sceneiy, and few trees. 
At Enniskillen the Upper Loch Erne is joined to the 
Lower by two streams crossed by bridges, and the 
town stands in the island formed by them. The road 
firom Enniskillen to Ballyshannon is exceedingly 
beautiful. Views of Loch Erne, studded with green 
islands, and bounded by blue mountains, to the east ; 
on the west and south, hills covered in some parts 
with wood, and exhibiting in most parts trees just 
beginning to throw out young shoots from their lopped 
trunks. About Church Hill, to the north, a small 
lake, surrounded by very grand mountain scenery, 
indented rocks, disposed in some parts in horizontal 
layers, forming the western boundary; green moun- 
tains, presenting here and there blue and yellow ditb ; 
and in the distance a great surface of bare rock, not 
less than 700 or 800 feet above the lake. The moun- 
tains on the south extending from the Upper Loch 
Erne to Sligo, all similar in form, and presenting im- 
mense layers of rocks, having bright green slopes at 
their bases, and immense gulleys cut from the top to 
the bottom. Their outline is made up of straight and 
jagged lines; their side often nearly perpendicular, 
and the highest probably considerably above 2000 feet 
The first view of Loch Erne is at about five miles from 
Church Hill. Here the mountain clifis of Leitrim 
form a grand outline to the south ; and the mountains 
of Fermanagh, composed of irregular masses of bright 
brown rock, covered with heath, and at the feet green 



JOURNAL OF A TOUE IN IRELAND. 153 

with grass, appear to the north and east, rising boldly 
out of the liJ^e's wooded promontories ; hills repose 
beyond them, and the great expanse of water is broken 
by an immense number of islands, all of soft and 
curved forms, and for the most part finely wooded ; in 
the northern distance, the blue mountains of Fer- 
managh, and further west, those of Donegal. 

The Erne runs rapidly over dark layers of rock 
into the sea at fiallyshannon ; its banks are but little 
wooded, but it is a noble river, a succession of small 
cataracts; and its last and greatest Ml is a wild and 
sublime scene. The river precipitates itself over 
jagged, broken, stratified rocks, into the Atlantic: 
white foam, and brown water, and black rock, and 
the blue sea, are the prime objects: the scene is 
the more impressive from the simplicity of its parts. 
From the hill above Ballyshannon appear, to the south, 
the hills of Sligo and of Leitrim, bold and fantastic 
in form ; Benvallen, a pyramidical mountain, appear- 
ing almost immediately above the town, and yet it is 
said to be twenty miles distant: Cape Tillen, to the 
west, a noble mass of mountain, grand and indistinct ; 
the hills to the north of veiy fine outlines, and co- 
louring bright brown, bare, and apparently producing 
nothing but moss. 

The road firom Ballyshannon to Donegal over green 
hiUs; no trees. The bare rocks and mountains having 
their summits sometimes disclosed, and sometimes 
hidden in mist, in the background. The river £sk, 
a fine mountain torrent; but without wood on its 
banks, and having nothing to recommend it but the 
wildness of its surrounding scenery. 

2. People more civilised than in the midland 
counties, or in Kerry; better dressed, and more 
h5 



154 /OmiKAL 09 A TO0R IH lUfiLAlTO. 

beauty of pereon. Protestants becoming mord im* 
merous as we advanced further north ; still consider^ 
able religious feuds. We passed from Beltarbet to 
Enniskillen on the I2th of Julj, the day of Sang 
William's triumph, and we heard and saw much riot; 
processions of men with tlie orange lily in their 
hats, women wearing this flower as a nosegay. The 
Hberty of wearing it interdicted to the CaUioKcs; a 
sign by which the Orangemen are still known. At 
night there is generally a battle between the two par- 
ties. The Catholic soktiers at Enniskillen, tlie Li« 
merick militia, did not fire on this day, but the Pro- 
testant regiments always do. Ballyshamnon is a truly 
Irish town — high houses, good in exterior, wretched 
internally; peats stopping up the windows: broken 
glass ; no sashes to be fbund. 

8. Course of crops. — Potatoes, oats, barley: this 
about Loch Erne. Further north a more enlight- 
ened system. At Ramekon, in Donegal, potatoes^ 
barley, oats, flax. After seven years, usually a fallow ; 
tben grass seed is sown, and tlH^e years taken in 
grass. Manure with the potatoes, never with the 
flax. Shell-sand used, particularly after fiillow. Flax 
the staple commodity of the country. 

Geology cf Fermainagk^ Gaoon, Leitrim, Donegal^ 
In Cavan, about Ballinagfat, a granitic schistose 
country. The granite associated with grawak^ schist 
and porphyry, and probably of the first &mily of se- 
condary rock. The schist, composed of compact felspar 
and chlorite, with a little mica : the porphyry having a 
base of compact felspar, and much decomposed, and 
where decomposed white. Beyond Cavan the second- 
aiy strata again occur, and continue to Ballyshannon, 



JOUBKAL OF A TOUB IH IBBLANB. 165 

vheie the firat micaceons schist in the west and nofth 
of Ireland occura, at least as &r as our knowledge ex- 
tends. Limestone and sandstone at Belturbet; lime** 
stone dipping to the west^ and abounding in shells and 
coral of different kinds; limestone occupying the greal* 
est part of the subsoil in the road to Enniskillen, and an 
immense number of layers, in general parallel to the 
horizon. At Church Hill, cli£& of a limestone of con- 
siderable consolidation* The mountains of Leitiim, 
composed of parallel layers of limestone and sandstone ; 
basaltic bolder-stones, probably from dyke& 

AtBallyshannon the Erne falls over limestone rocks, 
and a fine crystallised magnesian limestone occupies the 
lowest strata on the banks of the Erne ; and this lime- 
stone contains rhomboidal spathose crystals, and quartz 
crystals, in great abundance ; and above it is a limestone 
full of corals, alternating with a carbonaceous shale, but 
no coal visible. Coal will probably be found in abund- 
ance in the lowest part of the Leitrim mountain^ as the 
strata are of the carboniferous fiimily . 

The high mountains of Donegal are, probably, all 
micaceous schist, or granite, or sienite, at least in this 
part 

In the mountain road through the Bamesmore-gap, 
high mountains of granite, with comparatively little 
mica, constratified and massy in formation. Lower, 
micaceous schist, of beaudful varieties; a number. of 
q)ecies of gneiss ; tumblers of trap and sienite ; a few 
quartz veins in the granite, and some veins of quartz 
nod of calcareous spar in the gneiss above Donq;al : no 
chlorite, metalliferous indications in these mountains." 

Donegal, Jnly 10. 

JSameUon. — Road from Ballyshannon to Donegal 
exceedingly wild; rude mountains to the north and 



156 JOURNAL OF A TOUB IN IRELAND. 

west; green hills around the course of road; views of 
Cape Tillen^ and of the mountain capes stretching into 
the Atlantic, and the mountains of Leitrim souths stra- 
tified, and presenting a striking contrast to the rude 
massive rocks of DonegaL 

At Balljbofej, the river Finn, a large mountain 
stream, at this time brown from floods ; wooded hills on 
the west; bare brown curved hiUs on the east and 
north-east From Ballybofey to Litterkenny, a very 
wild road ; a great chain of mountains to the north and 
north-west ; the Arrigle and MuckrisL The summit of 
Arrigle peaked, and rising acutely pyramidical ; that of 
Muokrish tabular. The valleys wild, and but little cul- 
tivated ; very few trees ; grey rock, heath, and the sides 
of guUeys covered with lively green herbage. 

From Ballybofey to Ramelton, a very fine and im- 
pressive assemblage of scenery. Loch Swilly, a fine 
expanse of salt water, bounded in firont by green habit- 
able hills ; a few groups of trees on the very edge of the 
water ; in the distance high and wild mountains ; two 
peculiar, marked in outline and height, tabular and 
rounded; the most northern, Ossian's Mount On the 
west and north, magnificent views of the Arrigle and 
Muckrish chain, indistinct, blue, rising amongst the 
clouds, which are rolling about their sides and summits ; 
irregular craggy hills, chiefly bare rocks, below them. 

Ramelton, seated on the banks of a beautiful river, 
immediately discharging itself into Loch Swilly ; trees 
on the banks of the water; distant mountains above, 
and parts of the loch, with its beautiful boundaries, vi- 
sible firom all the streets of the village. 

2. The best race of people that has appeared iq the 
eourse of the journey ; civility, with independence of 
spirit ; no marks of the broken reed of rebellion ; no 



JOURNAL OF A TOUR IN IRELAND. 157 

crouching, but much dignity and simplicity ; yet the 
potatoe grows even amongst the mountains of the Finns, 
and the unquiet and uncertain spirit now and then 
breaks forth. I witnessed the humours of a crowd at 
Ramelton, assembled after having seen a pony race. A 
great number of men and women jostled together in the 
narrow streets of a little town, without any other object 
than that of pushing each other ; every room in eveiy 
house filled with people, enjoying whiskey and tobacco ; 
beggars, wherever there was a standing, or a sitting, or 
a lying place ; a number of drunken horse and foot pas- 
sengers; much finery of dress, but a number of persons, 
who seemed rather to have wished to appear magnifi- 
cent than to know how to produce the effect ; a pro- 
fiision of ribands and of white linens ; not much beauty 
of person. A great fight took place after the ftdr (an 
event that is always hoped for, and expected), and a 
number of heads were broken, and much bloody inflamed 
by whiskey, shed, but no lives absolutely lost ; one man 
was ' twice killed' by another, knocked down, and the 
head twice cut He was a Litterkenny boy, and had 
ofiTended the oppressing hero, by saying, ' Ay I and 
is not the boy of Latterkenny as good as the Ramelton 
boy, at cutting a bog or at heaving the peat ?' Many 
traditional stories of the giant race of the Finns, and 
their chieft^n, Finmacoul ; and Gaelic songs are said 
to be remembered and recited by the old men in the 
wild glens of Muckrish and Arrigle. 

3. Geology. — Granite and micaceous schist, and a 
great variety of sienites about Ballybofey. The incli- 
nation of the micaceous schist appeared to me to be 
uniformly to the north* Limestone about a mile boux 
Ballybofey ; carbonate of lime, with much mica, strar 
tified and directed to the north ; alternate layers, in the 



158 /OVRKAL OF A TOUR TJX IBEUlND. 

pxineipal qtuiny, of a compact siliceooB xo^k and crp* 
tallized carbonate of Ume, and, the carbonate of lime 
haying been wadied out at the sur&oe, the roek appears 
ribbed; much corvature, both of the siliceous rock and 
the marble veins of quartz and of calcareous spar cutting 
the limestone and specks of copper and much pyrites 
in the veins; lower is a more compact marble; the up- 
per marble is splintering in fracture, but this is nearer 
Carrara marble : this, probably, a great dyke of the 
same formation as the EiUamey marble, filling a chasm 
in the micaceous schist 

From Ballybojfey to Bamelton, a similar constitu* 
tion of country, similar inclination, curvature of strata, 
and immediately by Loch Swilly, great abundance of a 
micaceous schist, principally composed of quartz. 

In tibe mountains above Loch Foyle, and by Loch 
Salt, marble of elder formation, and a rock approaching 
very nearly to serpentine in its character, but composed 
of hornblende, felspar, and a little chlorite. The hij^ 
mountains about Loch Salt, sienite and quartz rock; 
no regular incliyMtion, but a distinct stratification, and 
much disturbance' and curvature : the limestone beds 
inclined to the south. 

Li the general arrangement about Loch Swilly, the 
micaoeoua schnst occupies the lowest position; above 
this is a stratified rock, principally consisting of marble, 
with a little mica, and exceedingly inourvated ; and upon 
these occur the beds of limestone, which, in several in^ 
stances, are in absolute contact and union with mica- 
ceous schist, and contain mica in abundance ; at the top 
of all, sienite of different kinds : the felspar and mica 
exceedingly white, and very decomposable: and quartz 
rocks crystalline, and having the greasy firacture. 

Muckriisth, said to be composed of quartz-rock. The 



JOUBKAL OF A TOUR IH IBEULND. 159 

quartzoee aand belongbg to it has probably resulted 
firom the decomposition of a compound rock of quarts 
and fekpar. 

The immense proportion of quartz in the moon-* 
tains of this district is a fact which can hardly be ex- 
plained by axij application, however forced, of the 
Huttonian theory. Pressure cannot interfere where the 
material is simple, and where no elastic matter is pie- 
sent; and to suppose any terrene solvent, which has 
afterwards been separated, will not coincide with the 
known laws of chemical affinity. 

Simday,Jiily 29. 

1. The morning of this day I spent in a ride to the 
mountain district of Donegal. From Ramelton to Nil- 
macrenan, wildness in the fore-ground, and in the back- 
ground bogs, and bare rocks in the valley. The sides 
of the hills only cultivated, and the summits partly co* 
loured, brown heath, and grey or white rock. 

At Loch Salt, three miles firom Nilmacrenan, a grand 
view. The Atlantic to the north-west, with a variety 
of salt-water lochs washing the feet of bleak moun- 
tains ; firesh-water lochs nearer, in the cavities of the 
mountains. Amongst these. Loch Salt wonderfully 
magnificent; breasted by a mountain to the east, at 
least a thousand feet high, and principally composed of 
rocks so white as to seem covered with snow; to the 
west, green hills with curved rocks, and a singular as- 
semblage of decomposed and water-worn stones ; and 
to the south an almost perpendicular precipice. 

From the summit of the mountain above Loch Salt, 
the wildest scene in Ireland, Muckrish and Arrigle, having 
their summits peeping above the clouds; distant, yet 
only so distant that the great gulleys of Arrigle and its 
yellow colouring were visible, and the dark heath of 



160 JOURNAL OF A TOUB IN IRELAND. 

Muckrish, and its white seams of sand: between the 
intermediate mountainsy precipices of rock, green hills, 
and dark lakes, with torrents pouring down the sides of 
mountains, whose summits were hidden in rain clouds. 
Sunshine appeared on some spots, whilst black clouds 
covered others ; and, in the space of ten minutes, the 
spot on which I stood had been wet and diy.* 

* [The following lines, descriptlTe of theK mountains, were, I beliere, 
written abont the same time as the above, as also those which succeed 
them, on Fair Head ; they are given as another example of the poetical 
temperament of the author, and of his disposition to express in verse 
what strongly impressed his mind : — "] 

Muckrish, and Arokil, ye pair 
Of mighty brethren, rising fair 

Amidst the summer evening's western light : 
Clouds might ye be, so bright your hue, 
So dense your purple in the blue 
That ushers in the night, 

Were ye not motionless ; your forms 
Unchanged by breezes or by storms, 

The same from day to day, from age to age, 
Unalter'd midst the wrecks of time. 
Scorning in giant strength sublime 

The whirlwind's and the lightning's rage. 

Summer's wild heathblasts, winter's snows, 
Disturb not your supreme repose : 

Not the mild influence of spring, 
Clothfaig the lowlands all in green, 
Creating round a Joyful scene 

Of change to you can bring. 

Not e'en the purple heath expands 
Its foliage o'er your blanched sands ; 

Your rocks alone the yellow lichen covers. 
In palest tints, and o'er the space ye own^ 
No shapes of life are known, 

Save where the eagle hovers. 

His screams, the mountain torrents' sound. 
The mountain breezes whistling round. 
The distant murmurs of the western wave, 



JOURNAL OF A TO0B IN IRELAND. 161 

2. Amongst these mQuntains, I met with a singular 
race of beings,-* the most gifted with vague curiosity of 
any men I have seen. They asked questions without 
considering whether they were civil or uncivil, and 
seemed little daunted by reproof. — Q. * Where do you 
come from ? ' -4. * Ramelton.' — * Do you belong there ? ' 

Compose the music wild and rade 
Of yoar anhaimted solitude, 
Blse silent as the gxETe. 

The glens that ranged around your feet 
In grand confusion seem to meet 

As with your parts to harmonise, 
While they your fountains drink, 
In kindred wildness sink 

As ye in wildness rise. 



But, chiefly thee. Fair Head! 
UnriTaU'd in thy form and majesty t 
Far on thy loftiest summit I have walked 
In the bright sunshine, while beneath thee roird 
The clouds in purest splendour, hiding now 
The ocean and his islands, parting now 
As if reluctantly ; whilst full in yiew 
The blue tide wildly roll'd, skirted with foam, 
And bounded by the green and smiling land. 
The dim pale mountains and the purple sky. 
Majestic cliff! thou birth of unknown time, 
Long had the billows beat thee, long the waves 
Rush'd o'er thy hoUow'd rocks, ere life adom'd 
Thy broken surface, ere the yellow moss 
Had tinted thee, or the wild dews of hearen 
Clothed thee with Terdure, or the eagles made 
Thy caves their aery. So in after time 
Long Shalt thou rest unaltered mid the wreck 
Of all the mightiness of human works ; 
For not the lightning, nor the whirlwind's force. 
Nor all the waves of ocean shall prevail 
Against thy giant strength, and thou shalt stand 
Till the Almighty voice which bade thee rise 
ShaU bid thee iUl. 



162 JOURNAL OP A TOUR IN IRELAND. 

' No.'—* What place do you belong ? • ' London.'—* Is 
it war or peace ? ' « War.' — * Have the English lost 
any men ? ' * There has been no battle lately.' — ^ When 
was the last? ' * Lord Nelson's ; did you never hear of 
him ?' — * No. What is your name ? ' * It is a name 
you have never heard of, and never will hear of? '— ^ 
The dialect and accent not similar to the Irish, but 
rather pure English, with many interlardings of un- 
meaning expressions, the most favourite of which was 
' Teagues.' They all agreed that there were old men 
who knew the history of the Finns and Finn Macoul, 
in Gaelic; but no one could show me the abode of 
these sages. 

Four religions — a mountain religion (Covenanters), 
a Scotch kirk, a Romish church, and an English church. 
The kirk exceedingly troublesome, and great enemies 
to Sabbath-breakers. A man hot with whiskey, and 
with the Presbyterian spirit, took away my rod on Sun- 
day evening. The people of the town seemed to resent 
the injury, but rather too mildly. The people are in a 
state scarcely as yet prepared for improvement; the 
middling classes having rude hospitality, the lowest 
barbarous: gratitude, however, was striking. A boy 
applied to me for medicine ; I prescribed for him, gave 
him physic, and, what was better, money : his gratitude 
was of the nobler kind. It is only in towns that the 
lower classes are depraved. 

Newtown Umavaddy, July 94. 

1. The road from Ramelton to Raphoe exceedingly 
hilly, cultivated ; but bare stone walls, or mounds of 
earth, forming the enclosures* 

From Raphoe to Derry, for the iSrst seven or eight 
miles, nothing worthy of observation. Great hills with- 
out rocks, enclosed, and gentle in their declivities. 



JOURNAL OF A TOUB IK niELANO. 163 

Within four miles of Deny, a view of the Foyle, a 
great river ; here, indeed, an arm of the sea, affected 
by the tides: near Deny the banks wooded, and the 
^ole landlocked; the hills of Donegal and the difls 
of MacgiUigan in the back-ground. Deny a well-built 
and lively city; much business done, but I should c(m« 
ceive toe remote from the main ocean to admit of a 
quick navigation to the ports of the north of England 
or Scotland, and not likely to rival Belfiut 

From Deny to Newtown Limavaddy, the first four 
miles through a flat cultivated country, backed by the 
hills of Donegal, bounding Loch Foyle; gradually 
scenes of beauty appear, fine woods on the banks of 
the sea; Scotch fits in abundance, birch, oak, holly. 
The distances very grand. The blue face of Loch 
Foyle, bounded to the west by the grey misty land of 
Donegal, and to the east by the grand and elevated 
clifib of MacgiUigan, the bases of which smile with ver- 
dure and cultivation, and the summits of which abrupt 
cmgs firown banen, desolate, and exposed to all the 
storms of the north. Newtown Limavaddy beautifully 
situated on the banks of a little clear meandering river, 
and elevated upon a gentle hill : a plain beneath, with 
meads and light and beautiful woods; the near hills 
wooded, and mountains, with green sides and bare sum- 
mits, in the eastern distance. The amphitheatre of 
mountains all of peculiar characters, and the character 
of the eastern chain marking a new country; a long 
line of ascent firom the north, and a rapid declivity 
towards the south. 

2. The micaceous schist extends on the banks of 
the river of Newtown Limavaddy, having similar cha- 
racters to those which it possesses in Donegal Here, 
at Newtown Limavaddy, rises the great basaldc cliff 



164 JOUBITAL OF A TOUB IN IRELAND. 

of Renavenac. No point of junction of this district 
with the schistose district appears. The summit of 
Renavenac is composed of a number of layers of ba- 
salt, rude in their formSy and grand in their outlines. 
Below the face of the cliff aie irregular crags, contain- 
ing an immense number of zeolites ; zeolites, agate, and 
calcareous spars are found in all the cavities of the 
basalt, the cliff can scarcely be less than 2000 feet 
above the level of the sea, and is exceedingly difficult 
of access. Small seams of coal are said to have been 
found at the base. A quarry of white limestone, with 
flints, has been broken in upon, and some scattered 
fragments of occur on both sides. The first 

regular exposed superposition of basalt, with regard to 
chalk, is to be found at a cliff about three miles to 
the north. This chalk is of the same degree of con- 
solidation as the lias limestone. Layers of single flints 
unaltered occur within six feet of it, and are seldom 
altered within two feet These layers of flints are 
usually about two feet or twenty-eight inches asunder, 
and are usually about twice the size of the fist. The 
chalk stratum appears here at about tiiirty feet in height, 
and is topped by basalt, from three to four hundred 
feet probably. Immediately above the chalk is a great 
layer of flint, four feet in thickness, with a red inter- 
mediate substance. Here the flints are either reddened, 
white, or crumbly in some of their parts, and the basalt 
at the point of contact is very decomposable. 

The stratification of these clifis is well marked. In 
one part these strata were distinct : — 

1. Irregular columnar basalt 

2. Small tabular schistose decomposing basalt 

3. Tabular basalt 

4. An ochreous stratum of small thickness. 



JOURNAL OF A TOUR IN IRELAND. 165 

5. Irregular tabular basalt, coming upon the flint in 
irregular outline. 

6. The flints generally red or white, and much frac- 
tured, with a soft ochreous substance between them. 

7. The chalk with its strata of flints declining to- 
wards the east, and lost about a mile off. The basalt 
likewise becomes lower towards the east, and the whole 
declination seems to be of this side. 

[Here may be introduced the author's sentiments 
relative to the natural advantages of Ireland, and its 
capacity for improvement, physically considered ; — ^they 
were expressed in a lecture introductory to a course on 
electro-chemical science, which he delivered at the Dublin 
Society in 1811 ; and arose out of reflections on the in- 
fluence of science on the best interests of a country.] 

Every part of the British dominions is interested in 
the progress of experimental science ; but no part ought 
to be in so high a degree interested as this island (Ire- 
land.) Its natural advantages are pre-eminent It con- 
tains an untouched fund of wealth, admirably situated 
for commercial intercourse with the whole world ; inter- 
sected by navigable rivers and lakes; supplied abun- 
dantly with ftiel, — ^possessing limestone prepared for the 
fire in every district — abounding in mineral treasures, 
^-coal and iron below ; and an inexhaustible source of 
manure upon the surface, — ^it needs only an enterprising 
spirit, directed by science, calling forth and awakening 
the industry of the people, to render it, in proportion to 
its extent, the most productive, the richest part of the 
empire. 

[His views relative to the political state of Ireland, 
founded on his own observations, are briefly and 



166 JOURNAL OF A TOUB IN IRELAND. 

forcibly expressed in a letter to his friend, Mr. 
Poole,] 

I long very much for the intercourse of a week with 
yon: I have very much to say about Ireland. It is aa 
island which might be made a new and a great country. 
It now boasts a fertile soil, an ingenious and robust 
peasantry, and a rich aristocracy ; but the bane of the 
nation, is the equality of poverty amongst the lower 
orders. All are slaves, without ihe probability of be- 
coming free ; they are in the state of equality which the 
Mons culottes wished for in France ; and; untU emulation 
and riches, and the love of clothes and neat houses are 
introduced amongst them, there will be no permanent 
improvement. 

Changes in political institutions can, at first, do little 
towards serving them: it must be by altering their 
habits, by diffusing manufactories, by destroying middle 
meUf by dividing fiurms, and by promoting industry, by 
making the pay proportional to the work : but I ought 
not to attempt to say anything on the subject, when my 
limits are so narrow ; I hope soon to converse with you 
about it. 

[Another letter to the same gentleman, in part ap- 
plicable to the state of Ireland, may be deserving of a 
place here.] 

To Thomas Poole, Esq. 
My dear Poole, 
What you have written concerning the indifference of 
men with regard to the interest of the species in future 
ages, is perfecdy just and philosophical ; but the greatest 
misfortune is, that men do not attend even to their own 
interest, and to the interest of their own age, in public 
matters. They think in moments, instead of thinking, 



JOURNAL OP A TOUB IN IBBLAND. 167 

as they ought to do^ in years; and they are guided by 
expediency, rather than by reason. Tlie true political 
maxim iS| that the good of the whole communi^^ is the 
good of every individual; but how few statesmen have 
ever been guided by this principle I In almost all go* 
vemments the plan has been to sacrifice one part of the 
community to other parts; sometimes the people to the 
aristocracy ; at other times, the aristocracy to the people ; 
sometimes the colonies to the mother country ; and at 
other times, the mother country to the colonies. A 
generous, enlightened policy, has never existed in 
Europe, since the days of Alfred ; and what has been 
called * the balance of power,' the support of civilization, 
has been produced only by jealousy, envy, bitterness, 
contest, and eternal war, either carried on by pens or 
cannon, destroying men morally and physically I But 
if I proceed in vague political declamation, I shall have 
no room left for the main object of my letter — ^your 
mine. I wish it had been in my power to write decid- 
edly on the subject; but your county is a peculiar one.* 
Such indications would be highly favourable in Corn- 
wall ; but in a shell limestone^ of late formation, there 
have, as yet, been no instances of great copper mines. I 
hope, however, that your mine will produce a rich store 
oifacts. 

Miners fi-om Alston Moor, or fi-om Derbyshire, would 
understand your country better than Cornish miners ; 
for the Cornish shifts are wholly different fix>m yours. 
It would be well for you to have some workmen at least 
from the. north, as they are well acquainted with shell 
limestone. 

The Ecton copper mine, in Staffordshire, is in this 
rock : it would be right for you to get a plan and his- 
* [Somenetshire.] 



168 JOURNAL OF A TOUR IN IRELAND. 

tory of that mine, which might possibly assist jour 
views. 

Had I been rich, I would adventure ; but I am just 
going to embark with all the little money I have been 
able to save, for a scientific expedition to Norway, Lap- 
land, and Sweden.* In all climes, 

I shall be your warm and sincere friend, 

H. Davy. 

* [This plan of trayel was not carried into effect at the time; but was 
in part realized many years after, as noticed in the preliminary yolnme.] 



ELEMENTS 

OP 

AGRICULTURAL CHEMISTRY, 

IN 

A COURSE OF LECTURES 

FOR 

THE BOARD OF AGRICULTURE; 

DBLIYERBD BETWEEN 1802 AND 1812. 



VOL. VIL 



[To MeMrs. Lottgmant and Co., the proprietors of the copyright of the 
Lectares on Agrienltoral Chemistrji the Editor has to express his thanks 
for the liherality with which they hare permitted him to include them 
in this collection. The fourth edition of the work is that which has been 
selected to be printed from, having had the last reylsion of the author. 

The dedication giren, is from the same edition ; the first was inscribed to 
the President and Members of the Board of Agriculture for the year 1812, 
at whose request the Lectures were first published '' as a testimony of the 
respect of the author, and of gratitude for the attention with which they 
have been received." The last was prompted by private feelings of regard 
and respect to a distinguished individual, between whom and the author 
for many years a friendship was maintained without interruption, of that 
beat kind, equidly valued by both. Mr. Knight has given expression to 
his sentiments towards the author, in a passage written in the most 
amiable and friendly manner, which has been introduced in the first 
volume. The author's towards Mr. Knight are not less forcibly pour- 
trayed in the letters which from time to time he wrote to him, during a 
period of at least twenty years. For the perusal of these, and for copies, 
the editor is indebted to the considerate Idndness of Mrs. Stackhouse 
Acton, from whom he is glad to learn that some of these letters are to be 
inserted in a memoir of the life of her late father, now preparing for 
publication. Had the editor seen them before, and in time, he would 
have considered it a duty to have inserted a selection from them, as 
they are very illustrative : at present he restricts himself to one, written 
after a very distressing event, the sudden death, from an accident, of 
Mr. E^night's only son, in the prime of manhood, full of promise of 
excellence (alluded to hi the first volume in page 468), depicting equally 
the strong emotions of grief and of the sympathy of the writer.] 

To Thomas Andbbw Knight, Esq. 

January nth, 1827. 
My Dear Sir, 
-I have three or four times within the last six weeks taken up the pen 
and begun to write to you ; but I have always bdd it down again, fearing 

I 2 



172 

to tniBt m3rBelf with a subject on which I could not write without feeling 
deeply, and great mental agitation. 

I have grieyed with you : in guch the most awful yisitation of eyU be- 
longing to human nature, it is almost Tain to attempt to offer consola- 
tion; yet considering life as a great system in which all is for good; and 
believing that the intellectual and moral part of our nature is as inde- 
structible as the atoms that compose our frames, I feel the conviction 
that when a mind so highly gifted and so little selfish is ronoved from 
this scene of being, apparently so prematurely, it is to act in a better 
and nobler state of existence. The noblest spirits often return soonest 
to the source of intellectual life from which they sprung ; and they az« 
surely the happiest ; whilst we are to await the trials of sorrow, sickness, 
and age. 

I was very grateful to your most amiable and angelic daughter, Mrs. 
Stackhouse, for a note that she wrote to me. Pray offer her my most 
sincere thanks. 

I offer my most ardent wishes for your recoveiy and that of Mrs. 
Knight. I know well the agony of ^^ipetfracta f but even in this case, 
time, the chief comforter, creates a new source of hope. 

I wish I could g^ve you a more satisfactory answer to your kind in- 
quiries respecting my health. Dr. Philip has been very kind to me, 
'' but my body does me sorely wrong." I sometimes hope and some- 
times despair of ultimate recovery. My paralytic symptoms are much 
diminished ; but stiU I cannot get rid of the stiffiiess in my left arm and 
leg. I am now amusing myself with Inquiries in natural history, and I 
hope in the spring to make some inquiries respecting the transmigrations 
of some of the angler's water-flies. 

The garden of the Zoological Society is flourishing, and there are a 
good many animals collected there. 

The political bark left by Mr. Canning without a pilot seems quite 
wrecked ; and I believe there will be some difficulty in building another. 
The country is in a very critical state, and there certainly never was a 
moment in which less political talent appeared ; but I am writing on a 
subject which every body seems alike ignorant of, and the business is, I 
fear, in hands weak in talent though strong in influence, 
I am, my dear sir, very sincerely. 

Your obliged friend, 

H. DAVY. 



TO 
THOMAS ANDREW KNIGHT, ESQ., F.R.S., 

PRBSIDBNT OF THB HORTICULTURAL SOCIBTT, 

THIS EDITION OF THB8B LBCTURB8 
19 IKSCRIBBD 

BY HIS FRIBUD, 

THE AUTHOR. 



ADYBRTISEMENT TO THE FOURTH EDITION. 

DuBiNQ ten years, from 1802 to 1812, 1 had the honour, 
every Session, of delivering Courses of Lectures before 
the Board of Agriculture. I endeavoured, at all times, 
to follow in them the prc^press of discovery; they, 
therefore, varied every year : and since they were first 
published, in 1813, some considerable improvements 
have been made in chemical science, which have ren- 
dered many alterations and additions necessary. 

I am indebted for much useful information to many 
gentlemen who have endeavoured to improve agricul- 
ture, and to apply scientific principles to this most im- 
portant of the arts ; of which, acknowledgments will be 
found in the body of the work. I hope there are no 
omissions on this head ; but should they exist, I trust 
they wlU be attributed to defect of recollection, and 
not to any want of candour or of gratitude. 

Where I have derived any specific statement from 
books, I have always quoted them; but I have not 
always made references to such doctrines as are become 
current, the authors of which are well known ; and 
which may be almost considered as the property of all 
enlightened minds. 

In revising this work for the fourth edition, I have 
been forcibly struck with its imperfections, and I regret 
that I have been able to do so little to render it more 
worthy of the approbation of those readers for whom it 



176 ADVEBTISEMENT. 

was designed. My object has been principally to dwell 
upon practical principles and practical applications of 
science ; and it is in the farm and not in the laboratory 
that these can be put to the test of experiment^ and my 
duties and pursuits have rendered it impossible for me 
to do more than point out the path of inquiry — to 
indicate the road to improvement The manner in 
which the work has been received, both in this country 
and the Continent, induces me to hope that its object 
however humble, has been to a certain extent attained, 
and that it has not been without its utility. 

I have retained an appendix containing an account 
of the experiments on grasses instituted by the Duke 
of Bedford at Wobum, because many of these experi- 
ments are alluded to in the body of the work. I am 
happy, however, to be able to refer my readers to a 
much fuller and more detailed account of this subject 
of investigation, in a treatise published by Mr. George 
Sinclair, entitled Hart. Gram. Wbburnensisy and which, 
from the nature of the details, and the singular modesty 
and clearness with which they are given, is well worthy 
the perusal of all persons interested in agricultural pur- 
suits. 

H. Davy. 

Park Street, Jan. 1, 1S87. 



ELEMENTS OP AGRICULTURAL CHEMISTRY. 



LECTURE I. 

Introductioii. — General Views of the Objects of the Coanei and of the 
Order in which they are to be discussed. 

It is with great pleasure that I receive the permission 
to address so distinguished and enlightened an audience 
on the subject of agricultural chemistry. 

That any thing which I am able to bring forward, 
should be thought worthy the attention of the Board 
of Agriculture, I consider as an honour ; and I shall 
endeavour to prove my gratitude, by employing ievery 
exertion to illustrate this department of knowledge, 
and to point out its uses. 

In attempting these objects, the peculiar state of the 
inquiry presents many difficulties to a lecturer. Agri- 
cultural chemistry has not yet received a regular and 
systematic form. It has been pursued by competent 
experimenters for a short time only: the doctrines have 
not as yet been collected into any elementary treatise ; 
and on an occasion when I am obliged to trust so much 
to my own arrangements, and to my own limited infor- 
mation, I cannot but feel diffident as to the interest that 
may be excited, and doubtful of the success of the un- 
dertaking. I know, however, that your candour will 
induce you not to expect any thing like a finished work 
upon a science as yet in its infancy ; and I am sure you 
will receive with indulgence the first attempt made in 

I 5 



178 AORIC0LTURAL CHEMISTRY. 

this coontry to illustrate it, by a series of experimental 
demonstrations. 

Agricultural chemistry has for its objects all those 
changes in the arrangements of matter connected with 
the growth and nourishment of plants ; the compara- 
tive values of their produce as food ; the constitution 
of soils ; the manner in which lands are enriched by 
manure, or rendered fertile by the different processes 
of cultivation. Inquiries of such a nature cannot but 
be interesting and important, both to the theoretical 
agriculturist, and to the practical farmer. To the first 
they are necessary in supplying most of the fundamen«- 
tal {Mrinciples on which the theory of the art depends. 
To the second they are useM in affording simple and 
easy experiments for directing his labours, and for 
enabling him to pursue a certain and systematic plan of 
improvement. 

It is scarcely possible to enter upon any investigation 
in agriculture without finding it connected, more or 
less, with doctrines or elucidations derived fix>m che- 
mistiy. 

If land be unproductive, and a system of ameliora- 
ting it is to be attempted, the sure method of obtaining 
the object is by determining the cause of its sterility, 
which must necessarily depend upon some defect in the 
constitution of the soil, which may be easily discovered 
by chemical analysis. 

Some lands of good apparent texture are yet sterile 
in a high degree ; and common observation and com- 
mon practice afford no means of ascertaining the cause, 
or of removing the effect. The application of chemical 
tests in such cases is obvious ; for the soil must contain 
some noxious principle, which may be easily discovered, 
and probably easily destroyed. 



LBCTUBB I. 179 

Are any of the saltfi of iron present ? they may be 
decompoeed by lime. Is there an excess of siliceous 
•and ? the system of improvement must depend on the 
application of day and calcareous matter. Is there a 
defect of calcareous matter? the remedy is obvious. Is 
an excess of vegetable matter indicated ? it may be 
removed by liming, paring, and burning. Is there a 
deficiency of vegetable matter? it is to be supplied by 
manure. 

A question concerning the different kinds of lime- 
atone to be employed in cultivation often occurs. To 
determine this fully in the common way of experience, 
would demand a considerable time, perhaps some years, 
and trials which might be injurious to crops ; but by 
simple chemical tests the nature of a limestone is dis* 
covered in a few minutes ; and the fitness of its appli- 
cation, whether as a manure for different soils, or as a 
cement, determined. 

Peat earth of a certain consistence and composition 
is an excellent manure ; but there are some varieties of 
peats which contain so large a quantity of ferruginous 
matter as to be absolutely poisonous to plants. Nothing 
can be more simple than the chemical operation for de- 
termining the nature, and the probable uses of a sub- 
stance of this kind. 

There has been no question on which more difference 
of opinion has existed, than that of the state in which 
manure ought to be ploughed into the land ; whether 
recent, or when it has gone through the process of fer- 
mentation ? and this question is still a subject of dis- 
cussion : but whoever will refer to the simplest princi- 
pies of chemistry, cannot entertain a doubt on the sub- 
ject As soon as dung begins to decompose, it throws 
off its volatile parts^ which are the most valuable and 



180 AGRICULTURAL CHEMISTRY. 

most efficient Dung which has fermented, so as to 
become a mere soft cohesive mass, has generally lo6t 
from one-third to one-half of its most useful constituent 
elements ; and, that it may exert its frill action upon 
the plant, and lose none of its nutritire powers, it 
should evidently be applied much sooner, and long 
before decomposition has arrived at its ultimate results. 

It would be easy to adduce a multitude of other 
instances of the same kind ; but sufficient, I trust, has 
been said to prove, that the connection of chemistry 
with agriculture, is not founded on mere vague specula- 
tion, but that it offers principles which ought to be un- 
derstood and followed, and which, in their progression 
and application, can hardly &il to be highly beneficial 
to the community. 

A view of die objects in this course of lectures, and 
of the manner in which they are to be treated, will not, 
I hope, be considered as an improper introduction. It 
will inform you what you are to expect ; it will afibrd a 
general idea of the connection of the different parts of 
the subject, and of their relative importance ; it will 
enable me to give some historical details of the pro- 
gress of this branch of knowledge, and to reason fi^m 
what has been ascertained, concerning what remains to 
be investigated and discovered. 

The phenomena of vegetation must be considered as 
an important branch of the science of organized nature ; 
but though exalted above inorganic matter, vegetables 
are yet in a great measure dependent for their existence 
upon its laws. They receive their nourishment fit>m 
the external elements ; they assimilate it by means of 
peculiar organs ; and it ^is by examining their physical 
and chemical constitution, and the substances and 
powers which act upon them, and the modifications 



LBCT0RE I. 181 

which they undergo, that the scientific principles of 
agricultural chenustry are obtained. 

According to these ideas, it is evident that the study 
ought to be commenced by some general inquiries into 
the composition and nature of material bodies, and the 
laws of their changes. The sur&ce of the earth, the 
atmosphere, and the water deposited firom it, must 
either together or separately afford all the principles 
concerned in vegetation; and it is only by examining 
the chemical nature of these principles, that we are 
capable of discovering what is the food of plants, and 
the manner in which this food is supplied and prepared 
for their nourishment The principles of the constitu- 
tion of bodies, consequently, will form the first subject 
for our consideration. 

By methods of analysis dependent upon chemical 
and electrical instruments discovered in late times, it 
has been ascertained that all the varieties of material 
substances may be resolved into a comparatively small 
number of bodies, which, as they are not capable of 
being decompounded, are considered in the present 
state of chemical knowledge as elements. The bodies 
incapable of decomposition at present known are fifty- 
two.* Of these forty are metals ; eight are inflamma- 
ble bodies ; and five are substances which unite with 
metals and inflammable bodies, and form with them 
acids, alkalies, earths, or other analogous compounds. 
The chemical elements acted upon by attractive powers 
combine in different aggregates. In their simpler com- 
binations, they produce various crystalline substances, 
distinguished by the regularity of their forms. In 
more complicated arrangements, they constitute the 

* [Now fifty-four ; since 1827 two new metals haye been discovered^ 
thorium by Berzelias, vanadium by Sefstrom.] 



182 AGRICtTLTCTBAL CHBMISTRY. 

▼arieties of regetable and animal sabstances^ bear the 
higher character of organization, and are rendered sob- 
aenrient to the purposes of life. And by the influence 
of heat, light, and electrical powers, there is a constant 
series of changes ; matter assumes new forms, the de- 
struction of one order of beings tends to the conservar 
tion of another ; solution and consolidation, decay and 
renovation, are connected ; and whilst the parts of the 
system continue in a state of fluctuation and change, 
the order and harmony of the whole remain unalterable. 

After a general view has been taken of the nature of 
the elements, and of the principles of chemical changes, 
the next object will be the structure and constitution of 
plants. In all plants there exists a system of tubes or 
vessels, which in one extremity terminate in roots, and 
at the other in leaves. It is by the capillary action of 
the roots that fluid matter is taken up from the soiL 
The sap in passing upwards becomes denser, and more 
fitted to deposit solid matter : it is modified by exposure 
to heat, light, and air in the leaves; descends through 
the bark, in its progress produces new oiganized mat- 
ter; and is thus, in its vernal and autumnal flow, the 
cause of the formation of new parts, and of die more 
perfect evolution of parts already formed. 

In this part of the inquiry, I shall endeavour to c<m- 
nect togeUier into a general view, the observations of 
the most enlightened philosophers who have studied 
the physiology of vegetation. Those of Grew, Mai- 
pighi, Sennebier, Darwin, De Candolle, Mirbel ; and, 
above all, of Mr. Knight : he is the latest inquirer into 
these interesting subjects, and his labours have tended 
most to illustrate this part of the economy of nature. 

The chemical composition of plants has, within the 
last ten years, been elucidated by the experiments of a 



LBCTUBS L 1S8 

number of chemical philo8ophen» both in this «od in 
other countries ; and it forms a beautiful part of gene- 
ral chemistry : it is too extensive to be treated of mi- 
nutely ; but it y/ill be necessary to dwell upon such 
parts of it, as afford practical inferences* 

If the oigans of plants be submitted to chemical ana- 
lysis, it is found that their almost infinite diversity of 
form depends upon different arrangements and com- 
binations of a very few of the elements ; seldom more 
thsn seven or eight bekmg to them, and three consti- 
tute the greatest part of their organized matter ; and 
according to the manner in which these dements are 
disposed, arise the different properties of the products 
of vegetation, whether employed as food, or for other 
purposes and wants of life. 

The value and uses of every species of agricultural 
produce are most correctly estimated and applied, when 
pnu^tical knowledge is assisted by principles derived 
from chemistry. The compounds in vegetables really 
nutritive as the food of animals, are very few; ferina or 
the pure matter of starch, gluten, sugar, vegetable jelly, 
oil, and extract. Of these the most nutritive is gluten, 
which approaches nearest in its nature to animal matter, 
and which is the substance that gives to wheat its supe- 
riority over other grain. The next in order as to 
nourishing power is oil, then sugar, then fiuina ; and 
last of all, gelatinous and extractive matters. Simple 
tests of the relative nourishing powers of the difibrent 
species of food, are the relative quantities of these sub- 
stances that they afibrd by analysis ; and though taste 
and appearance must influence die consumption of all 
articles in years of plenty, yet they are less attended 
to in times <^ scarcity, and on such occasions this kind 
of knowledge may be of the greatest importance. 



184 AGRICULTURAL CHEMISTRY. 

Sugar and farina, or starch, are very similar in compo- 
sition, and are capable of being converted into each 
other by simple chemical processes. In the discussion 
of their relations, I shall detail to you the results of 
some recent experiments, which will be found possessed 
of applications both to the economy of vegetation, and 
to some important processes of manufacture. 

All the varieties of substances found in plants, are 
produced from the sap ; and the sap of plants is derived 
from water, or from the fluids of the soil, and it is 
altered by, or combined with, principles derived from 
the atmosphere. The influence of the soil, of water^ 
and of air, will therefore be the next subject of con- 
sideration. Soils in all cases consist of a mixture of 
diflerent finely divided earthy matters; with animal or 
vegetable substances in a state of decomposition, and 
certain saline ingredients. The earthy matters are the 
true basis of the soil; the other parts, whether natural, 
or artificially introduced, operate in the same manner 
as manures. Four earths generally abound in soils; 
the aluminous, the siliceous, the calcareous, and the 
magnesian. These earths, as I have discovered^ consist 
of highly inflammable metals, united to pure air or 
oxygen ; and they are not, as fiur as we know, decom« 
posed or altered in vegetation. 

The great use of the soil is to afford support to the 
plant, to enable it to fix its roots, and to derive nourish- 
ment by its tubes slowly and gradually, from the soluble 
and dissolved substances mixed with the earths. 

That a particular mixture of the earths is connected 
with fertility, cannot be doubted : and almost all sterile 
soils are capable of being improved, by a modification 
of their earthy constituent parts. I shall describe the 
simplest method as yet discovered of analysing soils. 



LBCT0BB I. 185 

and of ascertaining the constitution and chemical ingre- 
dients which appear to be connected with fertility; and 
on this subject many of the former di£5culties of inves- 
tigation will be found to be removed by recent in- 
quiries. 

The necessity of water to vegetation, and the luxu- 
riancy of the growth of plants connected with the pre- 
sence of moisture in the southern countries of the old 
continent, led to the opinion so prevalent in the early 
schools of philosophy, that water was the great produc- 
tive element, the substance from which aU things were 
capable of being composed, and into which they were 
finally resolved. The *^ api<rrov iitv vStop " of the poet, 
^' water is the noblest,'' seems to have been an expres- 
sion of this opinion, adopted by the Greeks from the 
Egyptians, taught by Thales, and revived by the alche- 
mists in late times. Van Helmont, in 1610, conceived 
that he had proved, by a decisive experiment, that all 
the products of vegetables were capable of being gene- 
rated firom water. His results were shown to be falla- 
cious by Woodward in 1691 ; but the true use of water 
in vegetation was unknown till 1785; when Mr. Ca- 
vendish made the discovery, that it was composed of 
two elastic fluids or gases, inflammable gas or hydrogen, 
and vital gas or oxygen. 

Air, like water, was regarded as a pure element by 
most of the ancient philosophers ; a few of the chemical 
inquirers in the sixteenth and seventeenth centuries, 
formed some happy conjectures respecting its real na- 
ture. Sir Kenelm Digby, in 1660, supposed that it 
contained some saline matter, which was an essential 
food of plants. Boyle, Hook, and Mayow, between 
1665 and 1680, stated, that a small part of it only was 
consumed in the respiration of animals, and in the 



186 AORICULTUBAL CHEMISTRY. 

eombnstion of inflammable bodies; bat the tnie statical 
analysis of the atmosphere is comparatiTelj a recent 
labour^ achieved towards the end of the last century by 
Sdieele^ Priestley, and Lavoisier* These celebrated 
men showed that its principal elements are two gaaesy 
oxygen and azote, of which the first is essential to flame, 
and to the life of ajiimi^laj snd that it likewise contains 
small quantities ci aqueous vi^ur, and of carbonic 
acid gas ; and Lavoisier proved that this last body is 
itself a compound elastic fluid, consisting of charcoal 
dissolved in oxygen. 

Jethro Tull, in his treatise on Horse-hoeing, pub- 
lished in 1733, advanced the opinion, that minute earthy 
particles supplied the whole nourishment of the vege- 
table world ; that air and water were chiefly useful in 
producing these particles firom the land; and that ma- 
nures acted in no other way than in ameliorating the 
texture of the soil, in short, that their agency was 
mechanical This ingenious author of the new system 
of agriculture having observed the excellent efiects pro- 
duced in fimning, by a minute division of the soil, and 
the pulverization of it by exposure to dew and air, was 
misled, by carrying his principles too far. Duhamel, in 
a work printed in 1754, adopted the opinion of Tull, 
and stated, that, by finely dividing the soil, any number 
of crops might be raised in succession firom the same 
land. He attempted also to prove, by direct experi- 
ments, that vegetables of every kind were capable of 
being rdsed without manure. This celebrated horticul- 
turist lived, however, sufficiently long to alter his opi- 
nion. The results of his later and most refined obser- 
vations led him to the conclusion, that no single mate- 
rial afforded the food of plants. The general experience 
of fanners had long before convinced the unprejudiced 



LEcnmB I. 187 

of die tnith of the same o^nion, and that manures 
were absolutely consumed in the process of vegetation. 
The exhaustion of soUs, by carrying off com crops fix)m 
them^ and the effects of feeding cattle on lands, and of 
preserving their manure, offer fiimiliar illustrations of 
the principle ; and several philosophical inquirers, par- 
ticularly Hassenfratz and Saussure, have shown, by sa- 
tis&ctory experiments, that animal and vegetable mat- 
ters deposited in soils are absorbed by plants, and be* 
come a part of their organized matter. But though 
neither water, nor air, nor earth, supplies the whole of 
the food of plants, yet they all operate in the process of 
vegetation. The soil is the laboratoiy in which the 
food is prepared. No manure can be taken up by the 
roots of plants, unless water is present ; and water, or 
its elements, exist in all the products of vegetation. The 
germination of seeds does not take place without the 
presence of air or oxygen gas : and in the sunshine, 
vegetables decompose the carbonic acid gas of the at- 
mosphere, the carbon of which is absorbed, and becomes 
a part of their organized matter, and the oxygen gas, the 
odier constituent, is given off; and, in consequence of 
a variety of agencies, the economy of vegetation is made 
subservient to the general order of the system of nature. 
It is shown, by various researches, that the constitu- 
tion of the atmosphere has been always the same since 
the time that it was first accurately analysed ; and this 
must, in a great measure, depend upon the powers of 
plants to absorb or decompose the putrifying or decay- 
ing remains of animals and vegetables and the gaseous 
effluvia which they are constantly emitting. Carbonic 
acid gas is formed in a variety of processes of fermentar 
tion and combustion, and in the respiration of animals ; 
and as yet no other process is known in nature by which 



188 AOmCULTURAL CHEMISTRY. 

it can be consumed, except vegetadon. Animals pro- 
duce a substance which appears to be a necessary food 
of vegetables ; vegetables evolve a principle necessary to 
the existence of animals ; and these different classes of 
beings seem to be thus connected together in the exer- 
cise of their living functions, and to a certain extent 
made to depend upon each other for their existence. 
Water is raised from the ocean, difiused through the air, 
and poured down upon the soil, so as to be applied to 
the purposes of life. The different parts of the atmo- 
sphere are mingled together by winds or changes of 
temperature, and successively brought in contact with 
the surface of the earth, so as to exert their fertilizing 
influence. The modifications of the soil, and the appli- 
cation of manures, are placed within the power of man^ 
as if for the purpose of awakening his industry, and of 
calling forth his powers. 

The theory of the general operation of the more com- 
pound manures, may be rendered very obvious, by 
simple chemical principles ; but there is still much to 
be discovered, with regard to the best methods of ren- 
dering animal and vegetable substances soluble ; with 
respect to the processes of decomposition, how they may 
be accelerated or retarded, and the means of producing 
the greatest effects from the materials employed ; these 
subjects will be attended to in the Lectures on Ma- 
nures. 

Plants are found by analysis to consist principaUy of 
charcoal and aeriform matter. They give out, by dis- 
tillation, volatile compounds^; the elements of which are 
pure air, inflammable air, coally matter, and azote, or 
that elastic substance which forms a great part of the 
atmosphere, and which is incapable of supporting com- 
buftion. These elements they gain, either by their 



LECTURE I. 189 

leaves from the air, or by their roots from the soil. All 
manures from organized substances, contain the prin- 
ciples of vegetable matter, which, during putre&ction, 
are rendered either soluble in water or aeriform — and in 
these states they are capable of being assimilated to the 
vegetable organs. No one principle affords the pabulum 
of vegetable life ; it is neither charcoal, nor hydrogen, 
nor azote, nor oxygen alone ; but all of them together, 
in various states and various combination^ Organic 
substances, as soon as they are deprived of vitality, 
begin to pass through a series of changes, which ends 
in their complete destruction, in the entire separation 
and dissipation of the parts. Animal matters are the 
soonest destroyed by the operation of air, heat, and 
light. Vegetable substances yield more slowly, but 
finally obey the same laws. The periods of the appli- 
cation of manures from decomposing animal and vege- 
table substances, depend upon the knowledge of these 
principles; and I shaU be able to produce some new 
and important facts founded upon them, which, I trust, 
will remove all doubt from this part of agricultural 
theory. 

The chemistry of the more simple manures, the ma- 
nures which act in very small quantities, such as gyp- 
sum, alkalies, and various saline substances, has hitherto 
been exceedingly obscure. It has been generally sup- 
posed that these materials act in the vegetable economy, 
in the same manner as condiments or stimulants in the 
animal economy, and that they render the common food 
more nutritive. It seems, however, a much more pro- 
bable idea, that they are actually a part of the true food 
of plants, and that they supply that kind of matter to 
the vegetable fibre, which is analogous to the bony 
matter in animal structures. 



190 AQRICULTURAL CHEMISTRY. 

The opetatkm of gjpmim, it is \rell known, is ex- 
tremely capricious in this country, and no certain datm 
have ]]dtherto been offered for its application. 

There is, however, good ground for supposing that 
the subject will be fully elucidated by chemical inquiry. 
Those plants which seem most benefited by its applica^ 
tion, are plants which always afford it on analysis. 
Clover, and most of the artificial grasses, contain it ; 
but it exists in very minute quantity only in barley, 
wheat, and turnips. Many peat adiies, which are sold 
at a considerable price, consist in great part of gypsum, 
with a little iron; and the first seems to be their most 
active ingredient. I have examined several of the soik 
to which these ashes are successfiilly applied, and I 
have found in them no sensible quantity of gypsum. In 
general, cultivated soils contain sufficient of this sub- 
stance for the use of the grasses ; in such cases, its ap- 
plication cannot be advantageous. Fcnt plants require 
only a certain quantity of manure ; an excess may be 
detrimental, and cannot be useful. 

The theory of the operation of alkaline substances, is 
one of the parts of the chemistry of agriculture most 
simple and distinct. They are found in all plants, and 
therefore may be regarded as amongst their essential 
ingredients. From their powers of combination, like- 
wise, they may be useful in introducing various prin- 
ciples into the sap of vegetables, which may be subser- 
vient to their nourishment 

The fixed alkalies, which were formerly regarded as 
elementary bodies, it has been my good fortune to de- 
compose. They consist of pure air, united to highly 
inflammable metallic substances; but there is no reason 
to suppose that they are reduced into their elements in 
any of the processes of vegetation. 



LBCTURB I. 191 

In this part of the couxs^ I shall dwell at coxisiderable 
length on the important subject of lime, and I shall be 
aUe to offer some novel views. 

Slacked lime was used by the Romans for manuring 
the soil in which firuit«trees grew ; of this we are in* 
formed by Pliny. Marl had been employed by the 
Britons and the Gauls, from the earliest times, as a top- 
dressing for land. But the precise period in which 
burnt lime first came into general use in the cultivation 
of land, is, I believe, unknown* The origin of the ap- 
plication from the early practices, is sufficiently ob- 
vious ; a substance which had been used with success in 
gardening, must have been soon tried in forming ; and 
in countries where marl was not to be found, calcined 
limestone would be naturally employed as a substitute. 

The elder writers on agriculture, had no correct 
notions of the nature of lime, limestone, and marl, or of 
their effects ; and this was the necessary consequence of 
the imperfection of the chemistry of the age. Cal- 
careous matter was considered by the alchemists as a 
peculiar earth, which, in the fire, became combined 
with inflammable acid ; and Evelyn and Hartlib, — ^and, 
still later. Lisle, in their works on husbandry, have cha- 
racterised it merely as a hot manure of use in cold lands. 
It is to Dr. Black, of Edinburgh, that our first distinct 
rudiments of knowledge on the subject are owing. 
About the year 1755, this celebrated professor proved, 
by the most decisive experiments, that limestone and all 
its modifications, marbles, chalks, and marls, consist 
principally of a peculiar earth united to an aerial acid : 
that the acid is given out in burning, occasioning a loss 
of more than 40 per cent ; and that the lime in conse- 
quence becomes caustic 

These important facts immediately applied, with 



192 AGRICULTURAL CHEMISTRY. 

equal certainty, to the explanation of the uses of lime, 
both as a cement and as a manure. As a cement, lime, 
applied in its caustic state, acquires its hardness and 
durability, by absorbing the aerial (or, as it has been 
since called, carbonic) acid, which always exists in small 
quantities in the atmosphere; it becomes, as it were, 
again limestone. 

Chalks, calcareous marls, or powdered limestones, act 
merely by forming an usefiil earthy ingredient of the 
soil ; and their efficacy is proportioned to the deficiency 
of calcareous matter, which, in larger or smaller quan- 
tities, seems to be an essential ingredient of all fertile 
soils ; necessary, perhaps, to their proper texture, and as 
an ingredient in the organs of plants. 

Burnt lime, in its first effect, acts as a decomposing 
agent upon animal or vegetable matter, and seems 
to bring it into a state in which it becomes more 
rapidly a vegetable nourishment ;* gradually, however^ 
the lime is neutralised by carbonic acid, and converted 
into a substance analc^ous to chalk ; but in this case it 
more perfectly mixes with the other ingredients of the 
soil, is more generally diffused and finely divided ; and 
it is probably more useful to land than any calcareous 
substance in its natural state. 

The most considerable fact made known, with regard 
to limestone, within the last few years, is owing to Mr. 
Tennant It had been long known, that a particular 
species of limestone, found in difierent parts of the 
North of England, when applied in its burnt and 

* [This effect is qnesiioiiable ; from some experiments which I hare 
instituted, the results of which are described in the second Tolume of 
my Physiological and Anatomical Researches, lime appears to act as an 
antiseptic on animal and yegetable substances in general, and to preserre 
them, with the exception of cuticle, which it disoiganizes.] 



LECTURB Z. 193 

slacked state to land in. considerable quantities oc* 
casioned sterility, or considerably injured the crops for 
many years. Mr. Tennant, in 1800, by a chemical 
examination of this species of limestone, ascertained 
that it differed from common limestones by containing 
magnesian earth; and by several experiments he 
proved, that this earth was prejudicial to vegetation, 
when applied in large quantities in its caustic state. 
Under common circumstances, the lime from the mag- 
nesian limestone is, however, used in moderate quanti- 
ties upon fertile soils in Leicestershire, Derbyshire, and 
Yorkshire, with good efiect; and it may be applied in 
greater quantities to soils containing very large pro- 
portions of vegetable matter. Magnesia, when com- 
bined with carbonic acid gas, seems not to be preju* 
dicial to vegetation, and in soils rich in manure it is 
speedily supplied with this principle from the decom-* 
position of the manure. 

After the nature and operation of manures have been 
discussed, the next, and the last subject for our con* 
sideration, wiU be some of the operations of husbandry 
capable of elucidation by chemical principles. 

The chemical theory of faUowing is very simple. 
Fallowing affords a source of riches to the soil, in 
consequence of the absorption of oxygen and the aque- 
ous principles of the atmosphere, and so tends to pro- 
duce an accumulation of decomposing matter, which, 
in the common course of crops, would be employed as 
it is formed; yet in highly cultivated soils, under a 
regular succession of crops, properly manured, this prac- 
tice can rarely be advantageous ; and the cases in which 
it is really beneficial are for the destruction of weeds, 
and for cleansing foul soils. 
vol*. VIL K 



104 AGRICULTUEAL CHSMISTBT. 

The chemical theory of parmg and biumiiig, I shall 
discuss fuUy in this part of the Course. 

It is obvious^ that in all cases it must destroy a certain 
quantity of vegetable matter, and must be principally 
useful in cases in which there is an excess of ibis 
matter in soils. Burnings likewise^ renders clays leas 
odberenC, and in this way greatly improves their texture, 
and causes them to be less permeable to waiter. 

The instances in which it must be obvioudy preju* 
dicial are those of sandy dry siliceous soils, containing 
little animal or vegetable matter. Here it can only be 
destrucdre, for it decomposes that on which the sml 
depends for its prcductiTeness. 

llie advantages of irrigation, thoi]^h so lately a sub- 
ject of much attention, were well known to the ancients; 
and more than two oentuiies ago the practice was re- 
commended to the farmers of our country by Lord 
Bacon: '^ Meadow-watering," aoocording to the state- 
ments of this illustrious personage (given in his Natural 
History, in the article V^etation,) " acts not only by 
supplying useful moisture to the grass ; but likewise the 
water carries nourishment dissolved in it, and delfeads 
the roots from the ethcta of cold." 

No general prin^ples can be laid down respecting 
the comparative merit of the di£ferent systems of culti- 
vation and the various systems of crc^ adopted in 
different districts, unless the chemical nature of the 
soil, and the physical circumstances to which it is ex- 
posed, are fully known. Stiff coherent soils are those 
most benefited by minute division and aeration, and in 
the drill system of husbandry diese effects are produced 
to the greatest extent ; but still the labour and expense 
connected with its application in certain districts may 
not be compensated for by the advantages produced. 



LECTURE I. 195 

and there are some stiff soils whidi must be left in clods 
wiien sown with wheat Moist climates are best fitted 
ibr raising the artificial grasses, oats, and broad-leaved 
crops; stiff aluminous soils, in general, are most adapted 
for wheat crops ; and calcareous soils produce excellent 
sainfoin and cloyer. 

Nothing is more wanting in agriculture than experi- 
ments in which all the circumstances are minutely and 
scientifically detailed. This art will advance with 
rapidity in proportion as it becomes exact in its 
methods. As in physical researches, all the causes 
should be considered ; a difference in the results may 
be produced, even by the fall of a half inch of rain 
more or less in the course of a season, or a few de^ees 
of temperature, or even by a slight difference in the 
8ub-soil, or in the inclination of the land. 

Information collected after views of distinct inquiry 
would necessarily be fitted for inductive reasoning, and 
capable of being connected with the general principles 
of science ; and a few histories of the results of truly 
jdiilosophical experiments in agricultural chemistry 
would be of more value in enlightening and benefit- 
ing the &rmer, than the greatest possible accumulation 
of imperfect trials, conducted merely in the empirical 
spirit It is no unusual occurrence for persons who 
argue in favour of practice and experience to condemn 
generally all attempts to improve agriculture by philo- 
sophical inquiries and chemical methods. That much 
vague speculation may be found in the works of those 
who have lightly taken up agricultural chemistry, it is 
impossiUe to deny. It is not unccHnmon to find a 
number of changes rung upon a string of technical 
terms, such as oxygen, hydrogen, carbon, and azote, as 
if the science depended upon words rather than upon 

K 2 



196 AGKICULTURAL CHfiMISTRT. 

things. But this is, in fact, an argument for the ne* 
cessity of the establishment of just principles of 
chemistry on the subject Whoever reasons upon 
agriculture, is obliged to recur to this science. He 
feels that it is scarcely possible to advance a step with* 
out it ; and if he is satisfied with insulBBcient views, it 
is not because he prefers them to accurate knowledge, 
but generally because they are more current If a 
person journeying in the night wishes to avoid being 
led astray by the ignis fatuus, the most secure method 
is to carry a lamp in his own hand. 

It has been said, and undoubtedly with great truth, 
that a philosophical chemist would most probably make 
a very improfitable business of farming ; and this cer* 
tainly would be the case, if he were a mere philosophical 
chemist ; and unless he had served his apprenticeship 
to the practice of the art as well as to the theory. But 
there is reason to believe that he would be a more sue* 
cessfiil agriculturist than a person equally uninitiated in 
farming, but ignorant of chemistry altogether; his 
science, as far as it went, would be useful to him. Bat 
chemistry is not the only kind of knowledge required ; 
it forms a small part of the philosophical basis of agri- 
culture ; but it is an important part, and whenever ap- 
plied in a proper manner, must produce advantages. 

In proportion as science advances, all the principles 
become less complicated, and consequently more usefiiL 
And it is then that their application is most advantage- 
ously made to the arts. The common labourer can 
never be enlightened by the general doctrines of philo- 
sophy, but he will not refuse to adopt any practice, of 
the utility of which he is fully convinced, because it has 
been founded upon these principles. The mariner can 
trust to the compass, though he may be wholly unac- 



lECTUItB I. 197 

quainted with the discoveries of Gilbert on magnetism, 
or the refined principles of that science, developed by 
the genius of ^pinus. The dyer will use his bleaching 
liquor, even though he is perhaps ignorant not only of 
the constitution, but even of the name of the substance 
on which its powers depend. The great purpose of 
chemical investigation in agriculture ought undoubtedly 
to be, the discovery of improved methods of cultivation* 
But to this end general scientific principles and prac- 
tical knowledge are alike necessary. The germs of dis* 
covery are often found in rational speculations; and in- 
dustry is never so efficacious as when assisted by 
science. 

It is firom the higher classes of the community, firom 
the proprietors of land, — those who are fitted by their 
education to form enlightened plans, and, by their for* 
tunes, to carry such plans into execution : it is from 
these that the principles of improvement must flow to 
the labouring classes of the community; and in all 
classes the benefit is mutual; for the interest of the 
tenantiy must be always likewise the interest of the pro- 
prietors of the soiL The attention of the labourer will 
be more minute, and he will exert himself more for im- 
provement, when he is certain he cannot deceive his 
employer, and has a conviction of the extent of his 
knowledge. Ignorance in the possessor of an estate, of 
the manner in which it ought to be treated, generally 
leads either to inattention or injudicious practices in the 
tenant or the baili£P. '* Agrum pemmum muktari cujus 
Jiomnus nan docet sed audit vUUcumJ* 

There is no idea more unfounded than that a great 
devotion of time, and a minute knowledge of general 
chemistry, is necessary for pursuing experiments on the 
nature of soils or the properties of manures. Nothing 



198 AORICULTUBAL CHEMISTRY. 

can be more easy than to discover whether a soil effer- 
vesces, or changes colour by the action of an acid, or 
whether it bums when heated, or what weight it loses 
by heat ; and yet these simple indications may be of 
great importance in a system of cultivation. The ex- 
pense connected with chemical inquiries is extremely 
trifling ; a small closet is sufficient for containing all the 
materials required. The most important experiments 
may be made by means of a small portable apparatus ; 
a few phials, containing acids, alkalies, and chemical 
re-agents; some foil and wire of platinum; a lamp; a 
crucible; some filtrating paper; some funnels and 
glasses, for receiving products ; — ^are all that can be con** 
sidered as absolutely essential for pursuing useful re- 
searches. 

It undoubtedly happens in agricultural chemical ex- 
perimentSy conducted afler the most refined theoreticid 
views, that there are many instances of failure for one of 
success ; and this is inevitable, fi:om the capricious and 
uncertain nature of the causes that operate, and from 
the impossibility of calculating on all the circumstances 
that may interfere : but this is far from proving the in- 
utility of such trials ; one happy result, which can gene- 
rally improve the methods of cultivation, is worth the 
labour of a whole life; and an unsuccessful experiment, 
well observed, must establish some truth, or tend to re- 
move some prejudice. 

Even considered merely as a philosophical science, 
this department of knowledge is highly worthy of cul* 
tivation. For what can be more delightful than to trace 
the forms of living beings, and their adaptations and 
peculiar purposes ; to examine the progress of inorganic 
matter in its different processes of change, till it attain 



LECTURE I. 199 

its ultimate and highest destinatfon, — its subserviency 
to the purposes of man ? 

Many of the sciences are ardently pursued, and con- 
sidered as proper objects of study for all refined minds, 
merely on account of the intellectual pleasure they 
afford ; merely because they enlarge our views of na- 
ture, and enable us to think more correctly with respect 
to the beings and objects surrounding us. How much 
more, then, is this department of inquiry worthy of at- 
tention, in which the pleasure resulting from the love of 
truth and of knowledge is as great as in any other 
branch of philosophy, and in which it is likewise coa- 
nected with much greater practical benefits and advan- 
tages? ^^ i\SAi7 est melius, nihil nberiusy nihil fkmnne hbero 
diffniusJ* 

Discoveries made in the cultivation of the earth are 
not merely for the time and country in which they are 
developed, but they may be considered as extending to 
future ages, and as ultimately tending to benefit the 
whole human race ; as affording subsistence for genera- 
tions yet to come ; as multiplying life ; and not only 
multiplying life, but likewise providing for its enjoy- 
ment 



200 AGRICULTURAL CHEMISTRY. 



LECTURE II. 

Of the Oenenl Powers of Matter which inflaence Vegetation ; of Gravi- 
tation, of Cohesion, of Chemical Attraction, of Heat, of Light, of Elec- 
tricity; Ponderable Snbetances; Elements of Matter, particularly 
those found in Vegetables ; Laws of their Combinations and Arrange- 
ments. 

The great operations of the fiumer are directed 
towards the production or improvement of certiun 
classes of vegetables ; they are ^either mechanical or 
chemical, and are, consequently, dependent upon the 
laws which govern conimon matter. Plants them- 
selves are, to a certain extent, submitted to these 
laws ; and it is necessary to study their effects, both in 
considering the phenomena of vegetation, and the 
cultivation of the vegetable kingdom. 

One of the most important properties belonging 
to matter is graoitation, or the power by which masses 
of matter are attracted towards each other. It is in 
consequence of gravitation that bodies thrown into the 
atmosphere fall to the surface of the earth, and that 
the different parts of the globe are preserved in their 
proper positions. Gravity is exerted in proportion to the 
quantity of matter. Hence all bodies placed above the 
surface of the earth fall to it in right lines, which, 
if produced, would pass through its centre; and a body 
falling near a high mountain is a little bent out of the 
perpendicular direction by the attraction of the moun- 
tain, as has been shown by the experiments of Dr. 
Maskelyne on Schehallien. 



LBCTUEE IL 201 

Grayitation has a very important influence on the 
growth of plants; and it is rendered probable^ bj 
ihe experiments of Mr. Knight, that they owe the 
peculiar direction of their roots and branches almost 
entirely to this force* 

That gentleman fixed some seeds of the garden 
bean on the circumference of a wheel, which in 
one instance was placed vertically, and in the other 
horizontally, and made to revolve, by means of another 
wheel worked by water, in such a manner, that the 
number of the revolutions could be regulated; the 
beans were supplied with moisture, and were placed 
under circumstances favourable to germination. The 
beans all grew, notwithstanding the violence of re^ 
volution, which was sometimes as much as 250 revolu- 
tions in a minute on the vertical wheel, which always 
xevolved rapidly, and with little variation of velocity ; 
the radicles, or roots, pointed precisely in the direction 
of radii in whatever direction they were first placed. 
The germs took precisely the opposite direction, and 
pointed to the centre of the wheel, where they soon 
met each other. Upon the horizontal wheel, the con- 
flicting operation of gravitation and centrifiigal force 
occasioned the germs to form a cone, more or less 
obtuse, according to the velocity of the wheel, the 
radicles always taking a course diametrically opposite to 
that taken by the germs, and, consequently, pointing as 
much below as the germs pointed above the plane of 
the wheel's motion. 

These facts afford a rational solution of this curious 
problem, respecting which diffiBrent philosophers have 
given such different opinions ; some referring it to the 
nature of the sap, as De la Hire ; others, as Darwin, to 
the living powers of the plant, and the stimulus of 

k5 



202 AGRICULTUEAt CHEMISTRY. 

air upon the leaves, and of moisture upon the roots. 
The effect is now shown to be connected with me* 
chanical causes; and there seems no other power 
in nature to which it can with propriety be referred, 
but gravity, which acts universally, and which must 
tend to di^)ose the parts to take a uniform direction.* 

If plants in general owe their perpendicular di- 
rection to gravity, it is evident that the number of 
plants upon a given part of the earth's circumference 
cann6t be increased by making the surface irregular, 
as some persons have supposed. Nor can more stalks 
rise on a hill than on a spot equal to its base ; for the 
slight effect of the attraction of the hill, would be only 
to make the plants deviate a very little from the per- 
pendicular. Where horizontal layers are pushed forth, 
as in certain grasses, particularly such as the fiorin, 
lately brought into notice by Dr. Richardson, more 
food may, however, be produced upon an irregular 
sur&ce ; but the principle seems to apply strictly to 
corn crops. 

The direction of the radicles and germens is such, 
that both are supplied with food, and acted upon by 
those external agents which are necessary for their 
development and growth. The roots come in con- 
tact with the fluids in the ground; the leaves are 
exposed to light and air; and the same grand law 
which preserves the planets in their orbits is thus 
essential to the functions of vegetable life. 

When two pieces of polished glass are pressed 
together they adhere to each other, and it requires 

* Fig. 1. represents the case in which the horizontal wheel performed 
250 revolutions. 

Fig. 2. represents the form of the experiment when the yertical wheel 
was made to perform 150 revolutions in a minute. 



PL ATK. I. 



» r'O^. 



ruf I 



£ ^ 




Fi^ ? 




LECTURB II. 203 

some force to separate them. This is said to depend 
upon the attraction of cohesion. The same attract 
tion gives the globular form to drops of water, and 
enables fluids to rise in capillaiy tubes; and hence 
it is sometimes called capillary attraction. This at- 
traction, like gravitation, sterns common to all matter, 
and may be a modification of the same general force ; 
like gravitation, it is of great importance in vegetation. 
It preserves the forms of aggregation of the parts of 
plants, and it seems to be a principal cause of the 
absorption of fluids by their roots. 

If some pure magnesia, the calcined magnesia of 
druggists, be thrown into distilled vinegar, it gra- 
dually dissolves. This is said to be owing to chemical 
attraction, the power by which difierent species of 
matter tend to unite into one compound. Various 
kinds of matter unite with different degrees of force: 
thus sulphuric acid and magnesia unite with more 
readiness than distilled vinegar and magnesia; and 
if sulphuric acid be poured into a mixture of vinegar 
and magnesia, in which the acid properties of the 
vinegar have been destroyed by the magnesia, the 
vinegar will be set firee, and the sulphuric acid will 
take its place. This chemical attraction is likewise 
called chemical affinity. It is active in most of the 
phenomena of vegetation. The sap consists of a 
number of ingredients, dissolved in water by che- 
mical atiraction ; and it appears to be in consequence 
of the operation of this power, that certain principles 
derived from the sap are united to the vegetable 
organs. By the laws of chemical attraction, different 
]Hroduct8 of vegetation are changed, and assume new 
forms: the food of plants is prepared in the soil; 
vegetable and animal remains are changed by the 



201 A0RICULTI7BAL CHEMISTRY. 

action of air and water, and made fluid or aeriform; 
rocks are broken down and converted into soils; and 
soils are more finely divided and fitted as receptacles 
for the roots of plants. 

The difierent powers of attraction tend to preserve 
the arrangements of matter, or to unite them in new 
forms. If there were no opposing powers there would 
soon be a state of perfect quiescence in nature, a kind 
of eternal sleep in the physical world. Gravitation is 
continually counteracted by mechanical powers, by 
projectile motion, or the centrifiigal force; and their 
joint agencies occasion the motion of the heavenly 
bodies. Cohesion and chemical attraction are op- 
posed by the repulsive energy of heat^ and the har- 
monious cycle of terrestrial changes is produced by 
their mutual operations. 

Heat is capable of being communicated fix>m one 
body to other bodies; and its common effect is to 
expand them, to enlarge them in all their dimensions. 
This is easily exemplified. A solid cylinder of metal 
after being heated will not pass through a ring barely 
sufficient to receive it when cold. When water is 
heated in a globe of glass having a long slender neck, 
it rises in the neck ; and if heat be applied to air con- 
fined in such a vessel inserted above water, it makes its 
escape firom the vessel and passes through the water. 
Thermometers are instruments for measuring degrees of 
heat by the expansion of fluids in narrow tubes. Meiv 
cury is generally used, of which 100,000 parts at the 
fi*eezing point of water become 101,835 parts at the 
boiling point, and on Fahrenheit's scale these parts are 
divided into 180 degrees. Solids, by a certain increase 
of heat, become fluids, and fluids gases, or ela8tic:fluid& 
Thus ice is converted by heat into water, and by sdll 



LEGTUBE II. 20fi 

more heat it becomes steam ; and heat disappears, or, 
as it is called; is rendered latent, daring the conversion 
of solids into fluids, or fluids into gases, and re-appears, 
or becomes sensible, when gases become fluids, or fluids 
solids ; hence cold is produced during evaporation, and 
heat during the condensation of steam. 

There are a few exceptions to the law of expansion 
of bodies by heat, which seem to depend either upon 
some change in their chemical constitution, or on their 
becoming crystallised. Clay contracts by heat, which 
seems to be owing to its giving off water. Cast-iron 
and antimony, when melted, crystallize in cooling, and 
expand. Ice is much lighter than water. Water ex- 
pands a little, even before it freezes ; and it is of the 
greatest density at about 41'' or ^2% the freezing point 
being 32^; and this circumstance is of considerable im- 
portance in the general economy of nature. The in- 
fluence of the changes of seasons, and of the position of 
the sun on the phenomena of vegetation, demonstrates 
the effects of heat on the functions of plants. The 
matter absorbed from the soil, must be in a fluid state 
to pass into their roots ; and when the sui&ce is frozen, 
-they can derive no nourishment from it. The activity 
of chemical changes likewise is increased by a certain 
increase of temperature ; and even the rapidity of the 
ascent of fluids, by capillary attraction. 

This last £act is easily shown, by placing in each of 
two wine glasses a similar hollow stalk of grass, so bent 
as to discharge any fluid in the glasses slowly, by capil- 
lary attraction : if hot water be in one glass, and cold 
water in the other, the hot water will be discharged 
much more rapidly than the cold water. The fermen- 
tation and decomposition of animal and vegetable sub- 
stances require a certain degree of heat, which is con- 



206 AGRICULTURAL CHEMISTRY. 

sequently necessary for the preparation of the food of 
plants ; and, as evaporation is more rapid in proportion 
as the temperature is higher, the superfluous parts of 
the sap are most readily carried off at the time its ascent 
is quickest. 

Two opinions are current respecting the nature of 
heat By one School it is conceived to be a peculiar 
subtile fluid, of which the particles repel each other, but 
have a strong attraction for the particles of other mat* 
ter. By another it is considered as a motion or vibra* 
tion of the particles of matter, which is supposed to 
differ in velocity in different cases, and thus to produce 
the different degrees of temperature* Whatever deci* 
sion be ultimately made respecting these opinions, it is 
certain that there is matter moving in the space be* 
tween us and the heavenly bodies capable of communis 
eating heat; the motions of which are rectilinear: thus 
the solar rays produce heat in acting on the surface of 
the earth. The experiments of Sir W. Herschel have 
shown that the calorific effects of the solar rays bear no 
relation to their illuminating powers, the red rays pro- 
ducing a much greater effect of heat than any of the 
other coloured rays ; and it appears that there are vt^ 
viiible rays distinguished by very different degrees of 
refrangibility, some of which produce heat, and others 
of which are distinguished by their chemical effects. 

The different influences of the different solar rays on 
vegetation have not yet been studied ; but it is certain 
that the rays exercise an influence independent of the 
heat they produce. Thus plants kept in the dark, in a 
hot«house, grow luxuriantly, but they never gain their 
natural colours ; their leaves are white or pale, and their 
juices watery and peculiarly saccharine. 

The earth, when not exposed to the solar rays, is con- 



LECTURE II. 207 

fitaDtly losing heat by radiation, and different soils haye 
their temperature differently diminished by this cause. 

When a piece of sealing-wax is rubbed by a woollen 
cloth, it gains the power of attracting light bodies, suck 
as feathers or ashes. In this state it is said to be e&c- 
trical; and if a metallic cylinder, placed upon a rod of 
glass, is brought in contact with the sealing-wax, it like- 
wise gains the momentary power of attracting light 
bodies, so that electricity, like heat, is communicable^ 
When two light bodies receive the same electrical in- 
fluence, or are electrified by the same body, they repel 
each other. When one of them is acted on by sealing- 
wax, and the other by glass that has been rubbed by 
woollen, they attract each other ; hence it is said that 
bodies similarly electrified repel each other, and bodies 
dissimilarly electrified attract each other : and the electri- 
city of glass is called vitreous, or positive electricity, and 
that of sealing-wax resinous, or negative electricity. 

When, of two bodies made to rub each other, one is 
found positively electrified, the other is always found 
negatively electrified, and, as in the common electrical 
machine, these states are capable of being communi- 
cated to metals placed upon rods or pillars of glass. 
EHectricity is produced, likewise, by the contact of 
bodies ; thus a piece of zinc and of silver give a slight 
electrical shock when they are made to touch each 
other, and to touch the tongue ; and when a number of 
plates of copper and zinc, 100, for instance, are arranged 
in a pile with cloths, moistened in salt and water, in 
the order of zinc, copper, moistened cloth, zinc, copper, 
moistened cloth, and so on, they form an electrical bat- 
tery, which will give strong shocks and sparks, and 
which is possessed of remarkable chemical powers. The 
luminous phenomena, produced by common electricity, 



208 AGRICULTURAL CHEMISTRY. 

are well known. It would be improper to dwell upon 
them in this place. They are the most impressive 
effects occasioned by this agent ; and they offer illus- 
trations of lightning and thunder. 

Electrical changes are constantly taking place in na* 
ture, on the sur&ce of the earthy and in the atmosphere ; 
but as yet the effects of this power in vegetation have 
not been correctly estimated. It has been shown by 
experiments made by means of the Voltiuc batteiy (the 
instrument composed of zinc^ copper, and water), that 
compound bodies in general are capable of being de- 
composed by electrical powers ; and it is probable that 
the various electrical ^phenomena occurring in our sys- 
tem must influence both the germination of seeds and 
the growth of plants. I found that com sprouted much, 
more rapidly in water positively electrified by the Vol- 
taic instrument than in water negatively electrified ; and 
experiments made upon the atmosphere show that clouds 
are usually negative ; and as, when a cloud is in one 
state of electricity, the surface of the earth beneath is 
brought into the opposite state, it is probable, that in 
<:ommon cases the surface of the earth is positive. 

Different opinions are entertained amongst scientific 
men respecting the nature of electricity. By some the 
phenomena are conceived to depend upon a single sub- 
tile fluid in excess in the bodies said to be positively 
electrified, in deficiency in the bodies said to be nega- 
tively electrified. A second class suppose the effects to 
be produced by two different fluids, called by them the 
vitreous fluid and the resinous fluid; and an hypothe- 
sis has been advanced, in which they are considered as 
affections or motions of matter, or an exhibition of attrac- 
tive powers, similar to those which produce chemical 
combination and decomposition; but usually exerting 
their action on masses. 



LECTURE II. 209 

The powet which gives, to a bar or needle of steel the 
property of directing itself to two points of the. globe, 
called north and south poles, depends upon what is 
called magnetism. It agrees with electricity in many 
of its laws; but, as £EUr as our researches have hitherto 
gone, it is most active in its operation on metals and 
certain of their combinations. Iron, nickel, and cobalt, 
are most susceptible of magnetic impressions, and, in the 
harder compounds of iron, these impressions produce per- 
man^it effects ; but the recent experiments of M* Arago 
show, that copper, metals in general, and, probably, all 
other substances, receive very weak and evanescent mag^ 
netism, which seems to d^er in intensity for every 
body. Magnetism is capable of being communicated 
from bodies endowed with it to others that do not pos** 
sess it, and is produced whenever concentrated electri* 
ci^ passes through space, its sphere of action or com- 
munication being at right angles to the course of the 
electricity. Thus a bar of steel, placed transversely 
over a wire conveying an electrical shock, becomes a 
magnet. The connection of magnetism and electricity 
is of recent discoveiy, and the fact which served to 
establish it was made known by M. (Ersted, a Danish 
philosopher. It will ultimately probably tend to a more 
intimate acquaintance with the nature of these two ex- 
traordinary agents. The attractive powers of the mag- 
net may be made use of to show the existence of iron 
in soils, as will be mentioned more particularly here- 
after. 

The different powers that have been thus generally 
described continually act upon common matter so as to 
change its form, and produce arrangements fitted for 
the purposes of life. Bodies are either simple or com- 
pound. A body is said to be simple when it is in- 



210 AGRICULTURAL CHEMISTRY. 

capable of being resolved into any other forms of 
matter. Thus, gold or silver, though they may be 
melted by heat, or dissolved in corrosive menstrua, yet 
are recovered unchanged in their properties, and they 
are said to be simple bodies. A body is considered as 
compound, when two or more distinct substances are 
capable of being produced from it : thus marble is a 
compound body; for by a strong heat it is converted 
into lime, and an elastic fluid is disengi^ed in the 
process ; and the proof of our knowledge of the tme 
composition of a body is, that it is capable of being re* 
produced by the same substances as those into which it 
had been decomposed; thus by exposing lime for a long 
while to the elastic fluid disengaged during its calcina^ 
tion, it becomes converted into a substance similar to 
powdered marble, llie term element has the same 
meaning as simple or undeoompounded body ; but it is 
applied merely with reference to the present state of 
chemical knowledge. It is probable diat, as yet, we 
are not acquainted with any of the true elements of 
matter : many substances, formerly supposed to be 
simple, have been lately decompounded, and the 
chemical arrangement of bodies must be considered 
as a mere expression of facts, the results of accurate 
statical experiments. 

Vegetable substances in general are of a very com* 
pound nature, and consist of a great number of ele- 
ments, most of which belong likewise to the other king- 
doms of nature, and are found in various forms. Their 
more complicated arrangements are best understood 
after their simpler forms of combination have been ex- 
amined. 

The * number of bodies which I shall consider as at 
present undecomposed, are^ as wasstated in the intro- 



LECTURE n. 211 

dnctory lecture, five acidifying or solvent sobetances, 
eight inflammable bodies, and forty metals.* 

In most of the inorganic compounds, the nature of 
which is well known, into which these elements enter, 
they are combined in definite proportions ; so that, if 
the elements be represented by numbers, the pro- 
portions in which they combine are expressed either 
by those numbers, or by some simple multiples of them. 

I shall mention, in a few words, the characteristic 
properties of the most important simple substances, and 
the numbers representing the proportions in which they 
combine in those cases where they have been accurately 
ascertained. 

1. Oxygen forms about one-fifth of the air of our 
atmosphere. It is an elastic fluid, at all known tem* 
peratures. Its specific gravity is to that of air as 
10,967 to 10,000. It supports combustion with much 
more vividness than common air; so that if a small 
ateel wire or a watch-spring, having a bit of inflamed 
wood attached to it, be introduced into a bottle filled 
with the gas, it bums with great splendour. It is 
respirable. It is very slightly soluble in water. The 
number representing the proportion in which it com- 
bines is 15.t It may be made by heating a mixture of 
the mineral called manganese and sulphuric acid to- 
gether in a proper vessel, or by heating strongly red 
lead, or red precipitate of mercury. 

2. Chlorine is, like oxygen, a permanent elastic 
fluid. Its colour is yellowish green ; its smell is very 

* Now forty-two metals. Vide note p. 181. 

t [According to the most accurate estimate founded on experiments 
made since 1827, tiie number representing the proportion in which 
oxygen combines is 16, that of hydrogen being 2; supposing after the 
author, that water is composed of two proportions of hydrogen and of 
one of oxygen.] 



212 AGRICULTURAL CHEMISTRY. 

disagreeable ; it is not respirable ; it supports the comr- 
bustion of all the common inflammable bodies except 
charcoal ; its specific gravity is to that of air as 24,677 
to 10,000; it is soluble in about half its volume of 
water, and its solution in water destroys vegetable 
colours. Many of the metals (such as arsenic or 
copper) take fire spontaneously wben introduced into 
a jar or bottle filled with the ga& Chlorine may be 
procured by heating together a mixture of spirits of 
salt or muriatic acid, and manganese. The number 
representing the proportion in which this gas enters 
into combination is 67. 

3. Fluorine, or the fluoric principle. This substance 
has such strong tendencies to combination, that as yet 
no vessels have been found capable of containing it in 
its pure form. It may be obtained, combined with 
hydrogen, by applying heat to a mixture of fiuor, or 
Derbyshire spar, and sulphuric acid ; and in this state 
it is an intensely acid compound, a little heavier than 
water, and which becomes still denser by combining 
with water. The existence of fluorine as an element is 
proved by its expulsion from certain compounds by 
chlorine, and by its transference firom place to place. 
In attempts made to confine it, so as to examine its 
properties, it always combines with, or decomposes, the 
vessels employed; so that, as yet, its physical qualities 
are unknown: 16 is an approximation to the number 
representing it 

4. Iodine* His substance is procured fi'om the ashes 
of marine plants, after the extraction of the carbonate 
of soda, by acting upon them by sulphuric acid. It 
appears as a dark-coloured solid, having the colour and 
lustre of plumbago : its specific gravity is about 4 ; that 
of water being 1. It fuses at a low temperature, and at 



IBCTUKB II. 213 

a heat above that of boiling water becomes a violet* 
coloured gas. It forms an active acid by uniting to 
hydrogen. The allaUne metals bum, when heated 
in it It unites to all the metals upon wluch its action 
has been examined. 

5. Brome. This body has been very recently dis- 
covered in seap-water. It is in nature analogous to iodine, 
and resembles a compound of these two bodies. It is a 
dense liquid, and forms an orange-coloured gas by a 
gentle heat. 

6. Hydrogen^ or inflammable air, is the lightest known 
substance ; its specific gravity is to that of air as 732 to 
10,000. It bums by the action of an inflamed taper, 
when in contact with the atmosphere. The proportion 
in which it combines is represented by unity, or 1. It 
is procured by the action of diluted oil of vitriol, or 
hydro-sulphuric acid on filings of zinc or iron. It is the 
substance employed for filling air-balloons. 

7. Azote IB a gaseous substance, not capable of being 
condensed by any known degree of cold : its specific 
gravity is to that of common air as 9516 to 10,000. It 
does not enter into combustion under common circum-r 
stances, but may be made to unite with oxygen by the 
agency of electrical fire. It forms nearly four^fifths of 
the air of the atmosphere ; and may be procured by 
buming phosphoms in a confined portion of air. The 
number representing the proportion in which it com-» 
bines is 26. 

8. Carbon is considered as the pure matter of char- 
coal, and it may be procured by passing spirits of wine 
through a tube heated red. It has not yet been fused ; 
but rises in vapour at an intense heat. Its specific gra* 
vity cannot be easily ascertained ; but that of the diar 
moQd, which cannot chemically be distinguished firom 



214 AGRICULTURAL CHEMISTRY. 

pnre carixm is to that of water as 3500 to 1000. Char* 
coal has the remaxkable property of absorbing sevend 
times its Tolome of different elastic fluids, wbich are 
capd^ of being expelled from it by heat* The number 
representing it is 11*4. 

9. SwIphuT is die pure substance so well known by 
that name ; its specific gravity is to that of water as 
1990 to 1000. It fuses at about 220"" Fahrenheit ; and 
at between 500" and 600" takes fire, if in contact with 
the air, and bums with a pale blue flame. In this pro* 
eess it dissolves in the oxygen of the air, and produces a 
peculiar acid elastic fluid. The number representing it 
isSa 

10. Fhosphcnis is a solid of a pale red colour, of 
specific gravity 1770. It fuses at 90°, and boils at 
550^. It is luminous in the air at common tempera- 
tures, and bums with great violence at 150°, so that it 
must be handled with great caution. The number 
representing it is 222. It is procured by digesting to- 
gether bone-ashes and oil of vitriol, and strongly heat- 
ing the fluid substance so produced with powd^^ 
charcoal. 

1 1. Baron is a solid of a dark olive colour, infusible at 
any known temperature. It is a substance very lately 
discovered, and procured firom boracic acid. It buriMS 
with brilliant sparks when heated in oxygen, but not in 
chlorine. Its specific gravity, and the number repre- 
senting it, are not yet accurately known. 

12. Silicon is procured firom silica, or the earth of 
flints, by the acticm of potassium : it appears as a dark 
&wn«coloured powder, which is inflammd[)le, and which 
produces silica by combustion* It decomposes water 
and acids; and detonates ^en heated with alkaline 
carbonates. It is more analogous to boron in its proper- 



LECTUBB II. 215 

ties and cbemical habitades than to any other subetaaee. 
32 is an approximation to the number representing 
silicon.* 

13. Selenion^ or, as M. Berzelius, the discoverer^ 
names it, selenium, is a substance which forms a sort of 
intermediate link between the inflammable solids and 
the metals. It is semitransparent, of a red colour^ a 
nonconductcMT of electricity, of specific gravity about 
4300. 

14. Flatinum is one of the noble metals, of rather a 
doiier white than silver, and the heaviest body in 
natnre; its specific gravity being 21,500. It is not 
acted upon by any acid menstrua except such as con- 
tain chlorine; it requires an intense degree of heat for 
its fusion. 

15. The properties of gold are well known. Its spe- 
cific gravity is 19,277. It bears the same relation to 
acid menstrua as platinum : it is one of the characteristics 
of both these bodies, that they are very difficultly acted 
upon bysulphor. 

16. Siker is of specific gcwirity 10,400; it bums 
more readily than platinum or gold, which require the 
mtense heat of electricity. It r^wlily unites to sulphur. 
T%e number representing it is 205. 

17. Mercury is the only known metal fluid at the 
common temperature of the atmosphere ; it boils at 660^, 
and fireezes at 39^ below 0. Its specific gravity is 
13,560. The number representing it is 380. 

18. Copper is of specific gravity 8890. It bums when 
strongly heated, widi red flame, tinged with green. 
The number representing it is 120. 

19. Cobalt is of specific gravity 7700. Its point <rf 
fusion is very high, nearly equal to that of iron. In its 

♦ [Vide Vol. IV. p. 969.] 



816 AGRICULTURAL CHEMISTRY. 

calcined, or oxidated state, it is employed for giving a 
blue colour to glass. 

20. Nickel is of a white colour: its specific gravity is 
8820. This metal and cobalt agree with iron in being 
attractable by the magnet. The number representing 
nickel is 111. 

21. Iran is of specific gravity 7700. Its other pro- 
perties are well known. The number representing it is 
103. 

22. Tin is of Specific gravity 7291 ; it is a veiy fiisi- 
ble metal, and bums when ignited in the air: the num^ 
ber representing the proportion in which it combines is 
110. 

23. Cadmium is a newly discovered metal, very dmilar 
to tin in its sensible properties, of specific gravi^ about 
9000, and is very fiisible and volatile. 

24. Zinc is one of the most combustible of the com- 
mon metals. Its specific gravity is about 7210. It is 
a brittle metal under common circumstances; but when 
heated may be hammered or rolled into thin leaves, 
and after this operation is malleable. The number 
representing it is 66. 

25. Lead is of specific gravity 11,352; it fiises at 
a temperature rather higher than tin. The number, 
representing it is 398. 

26. Bismvth is a brittle metal, of specific gravity 
9822. It is nearly as fiisible as tin; when cooled 
slowly it crystallizes in cubes. The number represent- 
ing it is 135. 

27. Antimony is a metal capable of being volatilized 
by a strong red heat Its specific gravity is 6800. It 
bums, when ignited, with a faint white light* The 
number representing it is 170. 

28. Arsenic is of a bluish white colour, of specific 



LECTUKE IL 217 

gravity 8310. It may be procured by heating the 
powder of common white arsenic of the shops strongly 
in a Florence flask with oil. The metal rises in yapbur, 
and condenses in the neck of the flask. The number 
representing it is 90. 

29. Manganesvm may be procured firom the mineral 
called manganese, by intensely igniting it in a forge, 
mixed with charcoal powder. It is a metal very difiicult 
of fusion, and very combustible ; its specific gravity is 
6850. The number representing it is 177. 

30. Potassium is the lightest known metal, being 
only of specific gravity 850. It fiises at about 150^, 
and rises in vapour at a heat a little below redness. 
It is a highly combustible substance, takes fire when 
thrown upon water, bums with great brilliancy, and the 
product of its combustion dissolves in the water. The 
number representing it is 75. It may be made by 
passing fiised caustic vegetable alkali, the pure kali of 
dru^ists, through iron-turnings strongly ignited in a 
gun-barrel, or by the electrization of potash by a strong 
voltaic battery. 

31. Sodium may be made in a similar manner to 
potassium : soda, or the mineral alkali, being substi- 
tuted for the vegetable alkali. It is of specific gravity 
940. It is very combustible. When thrown upon 
water, it swims on its surface, hisses violently, and dis- 
solves, but does not inflame. The number represent- 
ing it is 88. 

32. Lithium is a metal procured fi'om a newly-dis- 
covered mineral^ alkali, very similar to sodium in its 
properties. 

33. Barium has, as yet, been procured only by 
electrical powers, and in very minute quantities, so 

VOL. vn. L 



218 AGRICULTURAL CHEMISTRY. 

that its properties have not been accurately examined. 
The number representing it appears to be 130. 

Strontium the 34th, Calcium the 35 th, Magnesium the 
36th, Aluminum the 37th, Zirconum the 38th, Gludnum 
the 39th, and Ittrium the 40th of the undecompounded 
bodies, like barium, have either not been procured 
absolutely pure or only in such minute quantities that 
their properties are little known; they are formed 
either by electrical powers, or by the agency of potas- 
sium, from the different earths whose names they bear, 
with the change of the termination in um ; and the 
numbers representing them are believed to be 90 
strontium, 40 calcium, 29 magnesium, 33 aluminum, 70 
zirconum, 39 glucinum. 111 ittrium. 

The remaining simple bodies are metals, most of 
which, like those just mentioned, can only be pro- 
cured with very great difficulty ; and the substances in 
general from which they are procured are very rare in 
nature. They are. Palladium, Rhodium^ Osmium^ Iri-- 
dium, Columbium, Chromium, Molybdenum, Cerium, 
Tellurium, Tungstenum, Titanium, Uranium. The 
numbers representing these last bodies have not yet 
been determined with sufficient accuracy to render 
a reference to them of any utility. 

The undecompounded substances unite with each 
other, and the most remarkable compounds are formed 
by the combinations of oxygen and chlorine with in- 
flammable bodies and metals ; and these combinations 
usually take place with much energy, and are asso- 
ciated with fire. 

Combustion, in fact, in common cases, is the process 
of the solution of a body in oxygen, as happens when 
sulphur, or charcoal is burnt ; or the fixation of oxygen 
by the combustible body in a solid form, which takes 



LECTURE II. 219 

place when most metals are burnt, or when phosphorus 
inflames ;. or the production of a fluid from both bodies, 
as when hydrogen and oxygen unite to form water. 

When considerable quantities of oxygen or of 
chlorine unite to metals or inflammable bodies, they 
often produce acids ; thus sulphurous, phosphoric, and 
boracic acids, are formed by a union of considerable 
quantities of oxygen with sulphur, phosphorus, and 
boron ; and muriatic acid gas is formed by the union 
of chlorine and hydrogen. 

When smaller quantities of oxygen or chlorine unite 
with inflammable bodies or metals, they form substances 
not acid, and more or less soluble in water ; and the 
metallic oxides, the fixed alkalies, and the earths, all 
bodies connected by analogies, are produced by the 
union of metals with oxygen. 

The composition of any compounds, the nature of 
which is well known, may be easily learned from the 
numbers representing their elements ; all that is neces- 
sary is to know how many proportions enter into union. 
Thus patassa, or the pure caustic vegetable alkali, con- 
sists of one proportion of potassium and one of oxygeo, 
and its constitution is, consequently, 75 potassium, 
15 oxygen. 

Carbonic acid is composed of two proportions of 
oxygen 30, and one of carbon 11*4. 

Again, Ume consists of one proportion of calcium and 
one of oxygen, and it is composed of 40 of calcium 
and 15 of oxygen. And carbonate of Kme^ or pure 
chalk, consists of one proportion of carbonic acid 41*4, 
and one of Ume 55. 

Water consists of two proportions of hydrogen 2, 
and one of oxygen 15 : and when water unites to other 

l2 



220 AGRICULTURAL CHEMISTRY. 

bodies in definite proportions, ^the quantity is 17, or 
some multiple of 17, t. e. 34 or 5 1^ or 68, &c. 

Soda, or the mineral alkali, contains two proportions 
of oxygen to one of sodium. 

Ammonia, or the volatile alkali, is composed of six 
proportions of hydrogen and one of azote. 

Amongst the earths. Silica^ or the earth of flints, 
probably consists of two proportions of oxygen to one 
of silicon ; and Magnesia, Stnmtia, Baryta^ or Barytes, 
Alumina, Zircona, Glucina, and Ittria, of one propor* 
tion of metal and one of oxygen. 

The metallic oxides in general consist of the metals 
united to firom one to four proportions of oxygen ; and 
there are, in some cases, many different oxides of the 
same metal : thus there are three oxides of lead ; the 
yellow oxide, or massicot, contains two proportions of 
oxygen ; the red oxide, or minium, three ; and the puce^ 
coloured oxide, four proportions. Again, there are tvoo 
oxides of copper, the black and the orange; the black 
contains two proportions of oxygen, the orange one. 

For pursuing experiments on the composition of such 
bodies as are connected with agricultural chemistry, a 
few only of the undecompounded substances are ne- 
cessary; and amongst the compounded bodies, the 
common acids, the alkalies, and the earths, are the 
most essential substances* The elements found in 
vegetables, as has been stated in the introductory lec- 
ture, are very few. Oxygen, hydrogen, and carbon 
constitute the greatest part of their organized matter. 
Azote, phosphorus, sulphur, manganesum, iron, silicum, 
calcium, aluminum, and magnesium, likewise in differ^ 
ent arrangements, enter into their composition, or are 
found in the agents to which they are exposed; and 
these twelve undecompounded substances are the ele- 



LECTURE II. 221 

ments, the study of which, is of the most importance to 
the agricultural chemist 

The doctrine of definite combinations^ as will be 
shown in the following lectures, will assist us in gain- 
ing just views respecting the composition of plants, and 
the economy of the vegetable kingdom; but the same* 
accuracy of weight and measure, the same statical re- 
sults, which depend upon the uniformity of the laws 
that govern dead matter, cannot be expected in opera- 
tions where the powers of life are concerned, and where 
a diversity of organs and of functions exist. The 
classes of definite inorganic bodies, even if we include 
all the crystalline arrangements of the mineral king- 
dom, are few, compared with the forms and substances 
belonging to animated nature. Life gives a peculiar 
character to all its productions; the power of attraction 
and repulsion, combination and decomposition, are sub- 
servient to it ; a few elements, by the diversity of their 
arrangement, are made to form the most different sub- 
stances; and similar substances are produced firom com- 
pounds which, when superficially examined, appear 
entirely different 



222 AGRICULTURAL CHEMISTRT. 



LECTURE IIL 

On the Organization of Plants. — Of the Roots, Trunk, and Branches. 
— Of their Structure. — Of the Epidermis. — Of the Cortical and Albur- 
noufl Parts. — Of Leayes, Flowers and Seeds. — Of the Chemical Con- 
stitution of the Organs of Plants, and the Substances found in them. 
— Of Mucilaginous, Saccharine, Eztractiye, Resinous and Oily Sub- 
stances, and other Vegetable Compounds ; their Arrangements in the 
Oiigans of Plants, their ComjKMition, Clianges, and Uses. 

Vabebtt characterises the vegetable kingdom; jet there 
is an analogy between the forms and the functions of 
all the different classes of plants^ and on this analogy 
the scientific principles relating to their organization 
depend. 

Vegetables are living structures, distinguished from 
animals by exhibiting no signs of perception, or of 
voluntary motion; and their organs are either organs 
of nourishment or of reproduction ; organs for the pre- 
servation and increase of the individual or for the multi- 
plication of the species. 

In the living vegetable system there are to be con- 
sidered, the exterior form, and the interior consti- 
tution. 

Every plant examined as to external structure, dis- 
plays at least four systems of organs — or some analo- 
gous parts. First, the Root Secondly, the Trunk cmd 
Branches, or Stem. Thirdly, the Leaves ; and, fourthly, 
the Flowers or Seeds, 

The root is that part of the vegetable which least 
impresses the eye; but it is absolutely necessary. It 



LECTURE III. 223 

attaches the plant to the surface^ is its organ of nourish- 
ment, and the apparatus by which it imbibes food from 
the soil. — The roots of plants, in their anatomical di- 
vision, are very similar to the trunk and branches. The 
root may indeed be said to be a continuation of the 
trunk, terminating in minute ramifications and fila- 
ments, and not in leaves. 

When the branch or the root of a tree is cut trans- 
versely, it usually exhibits three distinct bodies : the 
bark, the vfood, and the pith : and these again are indi- 
vidually susceptible of a new division. 

The bark, when perfectly formed, is covered by a 
thin cuticle, or epidermis, which may be easily sepa- 
rated. It is generally composed of a number of laminae 
or scales, which in old trees are usually in a loose and 
decaying state. The epidermis is not vascular, and it 
merely defends the interior parts from injury. In 
forest trees, and in the larger shrubs, the bodies of 
which are firm, and of strong texture, it is a part of 
little importance ; but in the reeds, the grasses, canes, 
and the plants having hoUow stalks, it is of great use, 
and is exceedingly strong, and in the microscope seems 
composed of a kind of glassy net-work, which is princi- 
pally siliceous earth. 

This is the case in wheat, in the oat, in different 
species of equisetum, and, above all, in the rattan, the 
epidermis of which contains a sufficient quantity of flint 
to give light when struck by steel; or two pieces rubbed 
together produce sparks. This fact first occurred to me 
in 1798, and it led to experiments, by which I ascer- 
tained that siliceous earth existed generally in the epi- 
dermis of the hollow plants. 

The siliceous epidermis serves as a support, protects 
the bark from the action of insects, and seems to per- 



224 AGRICULTURAL CHEMISTRY. 

form a part in the economy of these feeble vegetable 
tribes^ similar to that performed in the animal kingdom 
by the shell of the crustaceous insects. 

Immediately beneath the epidermis is the pcaren^ 
chyma. It is a soft substance^ consisting of cells^ filled 
with fluid, having almost always a greenish tint. The 
cells in the parenchymatous part, when examined by the 
microscope, appear hexagonal. This form, indeed, is 
that usually affected by the cellular membranes in 
vegetables, and it seems to be the result of the general 
reaction of the solid parts, similar to that which tales 
place in the honeycomb. This arrangement, which 
has usually been ascribed to the skill and artifice of the 
bee, seems, as Dr. Wollaston has observed, to be merely 
the result of the mechanical laws which influence the 
pressure of cylinders composed of soft materials, the 
nest of solitary bees being uniformly circular.* 

The innermost part of the bark is constituted by the 
cortical layers, and their numbers vary with the age of 
the tree. On cutting the bark of a tree of several 
years' standing, the productions of different periods may 
be distinctly seen, though the layer of every particular 
year can seldom be accurately defined. 

The cortical layers are composed of fibrous parts, which 
appear interwoven, and which are transverse and longi- 
tudinal. The transverse are membranous and porous, 
and the longitudinal are generally composed of tubes. 

The functions of the parenchymatous and cortical 
parts of the bark are of great importance. The tubes 
of the fibrous parts appear to be the organs that receive 
the sap ; the cells seem destined for the elaboration of 
its parts, and for the exposure of them to the action of 

* [This idea, was afterwards relinquished by Dr. Wollaston ; he re- 
tamed to the commonly received opinion on the subject.] 



PLATE 2. 




Fiif .J. 



LBCTUBE III. 225 

the atmosphere, and the new matter is annually pro- 
duced in the spring, immediately on the inner sur&ce 
of the cortical layer of the last year. 
. It has been shown by the experiments of Mr. Knight, 
and those made by other physiologists, that the sap de- 
scending through the bark after being modified in the 
leaves, is the principal cause of the growth of the tree : 
thus, if the bark is wounded the principal formation of 
new bark is on the upper edge of the wound; and when 
the wood has been removed, the formation of new wood 
takes place immediately beneath the bark: and every 
vessel and passage in the bark and wood of trees seems 
capable of carrying fluids in different and opposite direc- 
tions, though more readily and copiously in one direc- 
tion than in others, which offer something analagous to 
the anastomosis of vessels in animal bodies. A fact 
noticed by M. Palisot de Beauvois, is explained on this 
principle. That gentleman separated different portions 
of cortical layers from the rest of the bark in several 
trees, and found that in most instances the separated 
bark grew in the same manner as the bark in its natural 
state. The experiment was tried with most success on 
the lime-tree, the maple, and the lilac ; the layers of 
bark were removed in August 1810, and in the spring 
of the next year, in the case of the maple and the lilac, 
small annual shoots were produced in the parts where 
the bark was insulated.* 

The wood of trees is composed of an external part, 
called alburnum or sajhwood, and of an internal part, 
the heart-wood. The alburnum is white, and full of 
moisture, and in young trees and annual shoots it 
reaches even to the pith. The alburnum is the great 

* Fig. 3. represents the result of the expeiiineiit o& the maple. Jour- 
nal de Physique, September, 1811, p. 210. 

l5 



226 AGRICULTURAL CHEMISTRY. 

vascular system of the vegetable through which the 
sap rises, and the vessels in it extend from the leaves to 
the minutest filaments in the roots. 

There is in the alburnum a membranous substance^ 
composed of cells, which are constantly filled with the 
sap of the plant; and there are in the vascular system 
several difierent kinds of tubes; Mirbel has distin- 
guished four species — ^the simple tvbesy the porous tubesy 
the trachece, and the false trachece* 

The tubes which he has called simple tubes, seem to 
contain the resinous or oily fluids peculiar to difierent 
plants. 

The porous tubes likewise contain these fluids ; and 
their use is probably that of conveying them into the 
sap for the production of new arrangements. 

The tracheae contain fluid matter, which is always 
thin, watery, and pellucid ; and these organs, as well as 
the &lse tracheae, probably carry off water fi'om the 
denser juices, which are thus enabled to consolidate 
for the production of new wood. 

In the arrangement of the fibres of the wood, there 
are two distinct appearances. There are series of 
white and shining laminae, which shoot fi:om the centre 
towards the circumference, and these constitute what is 
called the silver grain of the wood. 

There are likewise numerous series of concentric 
layers, which are usually called the spurious grainy and 
their number denotes the age of the tree.f 

The silver grain is elastic and contractile ; and it has 

* Figs. 4, 5, 6y and 7, represent MirbeVs idea of the simple tubes, the 
porous tubes, the trachese, and the false trachece. 

t Fig. S. represents the section of an elm branch, which exhibits the 
tubular structure and the silver and spurious grain. Fig. 9. represents 
the section of part of the branch of an oak. Fig. 10. that of the branch 
of an ash. 



PLATE 3 



Fi^.^. 



- 2a6 




/? 226 



PLATE 4* 



Fi^ 9. 




^^^ 



TLATE. 5 



y ^ae. 



Fiff. JO. 







LECTURE III. 227 

been supposed by Mr. Knight, that the contractions 
produced in it by changes of temperature are the prin- 
cipal causes of the ascent of the sap. 

The silver grain is most distinct in forest trees ; but 
even annual shrubs have a system of fibres similar to 
it. The analogy of nature is constant and uniform, 
and similar effects are usually produced by similar 
organs. 

The pith occupies the centre of the wood ; its tex- 
ture is membranous; it is composed of cells, which 
are circular towards the extremity, and hexagonal in 
the centre of the substance. In the first infancy of 
the vegetable, the pith occupies but a small space. It 
gradually dilates, and in annual shoots and young trees 
offers a considerable diameter. In the more advanced 
age of the tree, acted on by the heart-wood, pressed by 
the new layers of the alburnum, it begins to diminish, 
and in very old forest trees becomes almost impercep- 
tible. 

Many different opinions have prevailed with regard 
to the use of the pith. Dr. Hales supposed that it was 
the great cause of the expansion and development of 
the other parts of the plant ; that being the most inte- 
rior, it was likewise the most acted upon of all the 
organs, and that fi:om its re-action the phenomena of 
their development and growth resulted. 

Linnaeus, whose lively imagination was continually 
employed in endeavours to discover analogies between 
the animal and vegetable systems, conceived '^ that the 
pith performed for the plant the same functions as the 
brain and nerves in animated beings." He considered 
it as the organ of irritability, and the seat of life. 

The latest discoveries have proved that these two 
opinions are equally erroneous. Mr. Knight has re- 



228 AGRICtTLTURAL CHEMISTRY. 

mored the pith in sereral young trees, and they con- 
tinued to live and to increase. 

It is evidently, then^ only an oigan of secondaiy 
importance. In early dioots, in Tigoioas growth, it is 
filled with moistore ; and it is a reserroir, perhaps of 
floid noorishment at the time it is most wanted. As 
the heart-wood forms, it is more and more separated 
6rom the living part, the albomum ; its functions be- 
come extinct, it diminishes, dies, and at last disappearsL 

The tendrili, the spines, and other similar parts of 
plants, are analogous in their organization to the 
branches, and offer a similar cortical and albumons 
organization. It has been shown, by the late observa- 
tions of Mr. Knight, that the directions of tendrils, and 
the spiral form they assume, depend upon the unequal 
action of light upon them ; and a similar reason has 
been assigned by M. De Candolle to account for the 
turning of the parts of plants towards the sun : that 
ingenious physiologist supposes that the fibres are 
shortened by the chemical agency of the solar rays 
upon them, and that, consequentiy, the parts will move 
towards the light 

The kavesj the great sources of the permanent 
beauty of vegetation, though infinitely diversified in 
their forms, are in all cases similar in interior organiza- 
tion, and perform the same fimctions. 

The alburnum spreads itself from the foot-stalks 
into the very extremity of the leaf; it retains its vascu- 
lar system and its living powers; and its peculiar tubes, 
particularly the tracheae, may be distinctly seen in the 
leaf.* 

* Fig. 11. represento part of a leaf of a yine magnified and cut, so as 
to exhibit the traches ; it is copied, aa are alao the preceding fignreB, 
from Orew's Anatomy of Plants. 



PLATE. 6. 



fiesa 



Ii^ Ji. 




LECTURE III. 229 

The green membranous substances may be con- 
sidered as an extension of the parenchyma, and the 
fine and thin covering as the epidermis. Thus the 
organization of the roots and branches may be traced 
into the leaves, which present, however, a more perfect, 
refined, and minute structure. 

One great use of the leaves is for the exposure 
of the sap to the influence of the air, heat, and light. 
Their surface is extensive, the tubes and cells very 
delicate, and their texture porous and transparent. 

In the leaves much of the water of the sap is 
evaporated ; it is combined with new principles, and 
fittted for its organizing functions, and probably passes, 
in its prepared state, firom the extreme tubes of the 
alburnum into the ramifications of the cortical tubes, 
and then descends through the bark. 

On the upper surface of leaves, which is exposed 
to the sun, the epidermis is thick but transparent, 
and is composed of matter possessed of little organi- 
sation, which is either principally earthy, or consists of 
some homogeneous chemical substance. In the grasses 
it is partly siliceous, in the laurel resinous, and in the 
maple and thorn it is principally constituted by a sub- 
stance analogous to wax. 

By these arrangements any evaporation, except firom 
the appropriated tubes, is prevented. 

On the lower surface the epidermis is a thin trans- 
parent membrane fiill of cavities, and it is probably 
altogether by this surface that moisture and the prin- 
ciples of the atmosphere necessary to vegetation are 
absorbed. 

If a leaf be turned, so as to present its lower surface 
to the sun, its fibres will twist so as to bring it as much 
as possible into its original position; and all leaves 



230 AGRICULTURAL CHEMISTRY. 

elevate themselves on the foot-stalk during their ex- 
posure to the solar light, and as it were move towards 
the sun. 

This effect seems, in a great measure, dependent 
upon the mechanical and chemical agency of light 
and heat. Bonnet made artificial leaves, which when a 
moist sponge was held under the lower sui&ce, and a 
heated iron above the upper surface, turned exactly in 
the same manner as the natural leaves. This, however, 
can be considered only as a very rude imitation of the 
natural process. 

What Linnssus has called the sleep of the leaves, 
appears to depend wholly upon the suspension of the 
action of light and heat, and on the operation of mois- 
ture. 

This singular but constant phenomenon had never 
been scientifically observed, till the attention of the 
botanist of Upsal was fortunately directed to it He was 
examining particularly a species of lotus, in which four 
flowers had appeared during the day, and he missed two 
in the evening; by accurate inspection, he soon dis- 
covered that these two were hidden by the leaves, which 
had closed round them. Such a circumstance could not 
be lost upon so acute an observer. He immediately 
took a lantern, went into his garden, and witnessed a 
series of curious facts before unknown. All the simple 
leaves of the plants he examined, had an arrangement 
totally different from their arrangement in the day : and 
the greater number of them were seen closed or folded 
together. 

The sleep of leaves is, in some cases, capable of being 
produced artificially. De CandoUe made this experi- 
ment on the sensitive plant. By confining it in a dark 
place in the day-time, the leaves soon closed ; but, on 



LECTURE III. 231 

illuminating the chamber with many lamps, they again 
expanded. So sensible were they to the effects of light 
and radiant heat. 

In the greater number of plants the leaves annually 
decay, and are re-produced; their decay takes place 
either at the conclusion of the summer, as in very hot 
climates, when they are no longer supplied with sap, in 
consequence of the dryness of the soU, and the evapo- 
rating powers of heat; or, in the autumn, as in the 
northern climates, at the commencement of the frosts. 
The leaves preserve their fiinctions, in common cases, 
no longer than there is a circulation of fluids through 
them. In the decay of the leaf, the colour assumed 
seems to depend upon the nature of the ehemical 
change ; and as acids are generally developed, it is 
usually either reddish-brown or yellow ; yet there are 
great varieties. Thus, in the oak, it is bright brown ; 
in the beech, orange ; in the elm, yellow ; in the vine, 
red ; in the sycamore, dark-brown ; in the cornel-tree, 
purple ; and, in the woodbine, blue. 

The cause of the preservation of the leaves of ever- 
greens through the winter, is not accurately known. 
From the experiments of Hales, it appears that the 
force of the sap is much less in plants of this species, 
and probably diere is a certain degree of motion in it, 
in warm days, even in winter; their juices are less 
watery than those of other plants, and probably less 
liable to be congealed by cold, and certainly not so easy 
of decomposition; and their vessels are defended by 
stronger coatings from the action of the elements. 

The production of the other parts of the plant takes 
place at the time the leaves are most vigorously perform- 
ing their functions. If the leaves are stripped off from a 
tree in spring, it uniformly dies ; and when many of the 



232 AGRICULTURAL CHEMISTRY. 

leaves of forest trees are injured by blasts, or long-con- 
tinued dryness, the trees always become stag-headed 
and unhealthy. 

The leaves are necessary for the existence of the in- 
dividual tree ; the flowers for the continuance of the 
species. Of all the parts of plants they are the most 
refined, the most beautiful in their structure ; and ap- 
pear as the master-work of nature in the TCgetable 
kingdom. The elegance of their tints, the Tariety of 
their forms, the delicacy of their organization, and the 
adaptation of their parts, are all calculated to awaken 
our curiosity, and excite our admiration. 

In the flower there are to be observed — 1st, the adyxj 
or green membranous part, forming the support for the 
coloured floral leaves. This is vascular, and agrees 
with the common leaf in its texture and oiganization ; 
it defends, supports, and nourishes the more perfect 
parts. 2d, The corolla, which consists either of a single 
piece, when it is called monopetalous ; or of many 
pieces, when it is called polypetalous. It is usually 
very vivid in its colours, is filled with an almost infinite 
Tariety of small tubes of the porous kind ; it incloses 
and defends the essential parts in the interior, and sup- 
plies the juices of the sap to them. These parts are, — 
3d, the stamens and the pistils. 

The essential part of the stamens are the summits or 
anthers, which are usually circular, and of a highly Tas* 
cular texture, and covered with a fine dust called the 
pollen. 

The pistil is cylindrical, and surmounted by the style; 
the top of which is generally round and protuberant.* 

In the pistil, when it is examined by the microscope, 

* Pig. 12. represents the common Ifly ; a the corolla, bbbbb the an- 
thers, c the pistil. 



PLATE 7 



p ^3S, 




LECTURE III. 233 

congeries of spherical forms may usually be perceived^ 
which seem to be the bases of the future seeds. 

It is upon the arrangement of the stamens and the 
pistils^ that the Linnaean classification is founded. The 
numbers of the stamens and pistils in the same flower, 
their arrangements^ or their division in different flowers, 
are the circumstances which guided the Swedish philo- 
sopher, and enabled him to form a system admirably 
adapted to assist the memory, and render botany of easy 
acquisition ; and which, though it does not always asso- 
ciate together the plants most analogous to each other 
in their general characters, is yet so ingeniously con- 
trived as to denote all the analogies of their most essen- 
tial parts. 

The pistil is the organ which contains the rudiments 
of the seed ; but the seed is never formed as a re-pro- 
ductive germ, without the influence of the pollen, or 
dust on the anthers. 

This mysterious impression is necessary to the con- 
tiniled succession of the different vegetable tribes. It is 
a feature which extends the resemblances of the different 
orders of beings, and establishes, on a great scale, the 
beautiful analogy of nature. 

The Ancients had observed that different date trees 
bore different flowers, and that those trees producing 
flowers which contained pistils, bore no fruit, unless in 
the immediate vicinity of such trees as produced flowers 
containing stamens. This long^stablished fact strongly 
impressed the mind of Malpighi, who ascertained se- 
veral analogous &cts with regard to other vegetables. 
Grew, however, was the first person who attempted to 
generalize upon them ; and much just reasoning on the 
subject may be found in his works. Linnaeus gave a 
scientific and distinct form to that which Grew had only 



234 AGRICULTURAL CHEMISTRY. 

generally observed, and has the glory of establishing 
what has been called the sexual system^ upon the basis 
of minute observations and accurate experiments. 

The seedy the last production of vigorous vegetation, 
is wonderfully diversified in form. Being of the highest 
importance to the resources of nature, it is defended 
above all other parts of the plant ; by soft pulpy sub- 
stances, as in the esculent fruits ; by thick membranes, 
as in the leguminous vegetables ; and by hard shells, or 
a thick epidermis, as in the palms and grasses. 

In every seed there is to be distinguished, 1. the 
arffan of nourishment; 2. the nascent plant, or the 
plume ; 3. the nascent root, or the radicle. 

In the common garden bean, the organ of nourish- 
ment is divided into two lobes called cotyledons; the 
plume is the small white point between the upper part 
of the lobes ; and the radicle is the small curved cone 
at their base.* 

In wheat, and in many of the grasses, the organ of 
nourishment is a single part, and these plants are called 
monocotyledonaus. In other cases it consists of more 
than two parts, when the plants are called polycotyledo- 
nous. In the greater number of instances, it is, how- 
ever, simply* divided into two, and is dicotyledonous. 

The matter of the seed, when examined in its com- 
mon state, appears dead and inert: it exhibits neither 
the forms nor the functions of life. But let it be acted 
upon by moisture, heat, and air, and its organized 
powers are soon distinctly developed. The cotyledons 
expand, the membranes burst, the radicle acquires new 
matter, descends into the soil, and the plume rises to- 
wards the free air. By degrees the organs of nourish- 

* Kg. Id. represents the g^den bean ; aa the cotyledons, b the plume, 
e the radicle. 



LECTUBE III. 235 

ment of dicotyledonous plants become vascular^ and 
are converted into seed leaves, and the perfect plant 
appears above the soil. Nature has provided the ele- 
ments of germination on every part of the surface ; 
water and pure air and heat are universally active, and 
the means for the preservation and multiplication of 
life are at once simple and grand. 

To enter into more minute details on the vegetable 
physiology would be incompatible with the objects of 
these Lectures. I have attempted only to give such 
general ideas on the subject as may enable the philo- 
sophical agriculturist to understand the functions of 
plants ; those who wish to study the anatomy of vege- 
tables, as a distinct science, will find abundant materials 
in the works of the authors I have quoted, page 182, and 
likewise in the writings of Linnaeus, Desfontaines, De 
Candolle, De Saussure, Bonnet, and SmitL 

The history of the peculiarities of structure in the 
different vegetable classes rather belongs to botanical 
than agricultural knowledge. As I mentioned in the 
commencement of this Lecture, their organs are pos- 
sessed of the most distinct analogies, and are governed 
by the same laws. In the grasses and palms, the cortical 
layers are larger in proportion than the other parts; 
but their uses seem to be the same as in forest trees. 

In bulbous roots, the alburnous substance forms the 
lai^est part of the vegetable ; but in aU cases it seems 
to contain the sap, or solid materials deposited from 
the sap. 

The slender and comparatively dry leaves of the pine 
and the cedar perform the same functions as the large 
and juicy leaves of the fig-tree, or the walnut. 

Even in the cryptogamia class, where no flowers are 
distinct, still there is every reason to believe that the 



236 AQRICULTUBAL CHBMISTRY. 

production of the seed is effected ia the same way as in 
the more perfect plants. The mosses and lichens^ which 
belong to this family, have no distinct leaves, or loot^ 
but they are furnished with filaments which perform the 
same functions ; and even in the fungus and the mush- 
room there is a system for the absorption and aeration 
of the sap. 

It was stated in the last Lecture, that all the different 
parts of plants are capable of being decomposed into a 
few elements. Their uses as food, or for the purposes 
of .the arts, depend upon compound arrangements of 
those elements which are capable of being produced 
either from their organized parts, or fix>m the juices 
they contain ; and the examination of the nature of 
these substances is an essential part of Agricultural 
Chemistry. 

Oils are expressed from the fruits of majij plants : 
resinous fluids exude from the wood ; saccharine mat- 
ters are afforded by the sap ; and dyeing materials are 
furnished by leaves, or the petals of flowers : but par- 
ticular processes are necessary to separate the different 
compound vegetable substances from each other ; such 
as maceration, infusion, or digestion in water, or in 
spirits of wine : but the application and the nature of 
these processes will be better understood when the che- 
mical nature of the substances is known ; the consi- 
deration of them will therefore.be reserved for another 
place in this Lecture. 

The compound substances found in vegetables are, 

1. gum, or mucilage, and its different modifications; 

2. starch; 3. sugar; 4. albumen; 5. gluten; 6. gum 
elastic; 7. extract; 8. tannin; 9. indigo; 10. colour- 
ing principles ; 11. bitter principles ; 12. wax; 13. re- 
sins; 14. camphor; 15. fixed oils; 16. volatile oils; 



LECTURE III. 237 

17. woody fibre; 18. acids; 19. alkalies, earths, me- 
tallic oxides, and saline compounds. 

I shall describe generally the properties and compo- 
sition of these bodies, and the manner in which they 
are procured. 

1. Gam is a substance which exudes firom certain 
trees ; it appears in the form of a thick fluid, but soon 
hardens in the air, and becomes solid: when it is 
white, or yellowish white, more or less transparent, and 
somewhat brittle, its specific gravity varies fi:om 1300 
to 1490. 

There is a great variety of gums, but the best known 
are gum arabic, g^m Senegal, gum tragacanth, and the 
gum of the plum or cherry tree. Gum is soluble in 
water, but not soluble in spirits of wine. If a solution 
of g^m be made in water, and spirits of wine or alcohol 
be added to it, the gum separates in the form of white 
flakes. Gum can be made to inflame only with diffi- 
culty ; much moisture is given ofi^ in the process, which 
takes place with a dark smoke and feeble blue flame, 
and a coal remains. 

The characteristic properties of gum are its easy 
solubility in water, and its insolubility in alcohol. Dif- 
ferent chemical substances have been proposed for ascer- 
taining the presence of gum, but there is reason to 
believe that few of them afibrd aociirate results; and 
most of them (particularly the metallic salts), which 
produce changes in solutions of gum, may be conceived 
to act rather upon some saline compounds existing in 
the gum, than upon the pure vegetable principle. 

Mucilage must be considered as a variety of gum ; it 
agrees with it in its most important properties, but 
seems to have less attraction for water. According to 
Hermbstadt, when g^m and mucilage are dissolved to- 



238 AGRICULTITRAL CHEMISTRY. 

getfaer in water, the mucilage may be separated bj 
means of sulphuric acid. Mucilage may be procured 
from linseed, from the bulbs of the hyacinth, from the 
leaves of the marshmallows, from several of the lichens, 
and from many other vegetable substances. 

From the analysis of MM. Gay Lussac and Thenard, 
it appears that gum arable contains, in 100 parts, 

Of carbon ... 42-23 

oxygen - - _ 50-84 

hydrogen - - _ 6*93 
With a small quantity of saline and 

earthy matter. 

Or, of carbon - - - 42*23 
Oxygen and hydrogen in the'J 

proportions necessary to form V 57*77 
water - - J 

This estimation agrees very nearly with the definite 
proportions of 11 of carbon, 10 of oxygen, and 20 of 
hydrogen. 

All the varieties of gum and mucilage are nutritious 
as food. They either partially or wholly lose their so- 
lubility in water, by being exposed to a heat of 500® 
or 600° Fahrenheit, but their nutritive powers are not 
destroyed, unless they are decomposed. Gum and 
mucilage are employed in some of the arts, particularly 
in calico-printing ; till lately, in this country, the calico- 
printers used gum arable ; but many of them, at the 
suggestion of Lord Dundonald, now employ the muci- 
lage from lichens. 

2. Starch is procured firom different vegetables, but 
particularly from wheat or from potatoes. To make 
starch from wheat the grain is steeped in cold water till 
it becomes soft, and yields a milky juice by pressure ; 



LECTUHE HI. 239 

it is then put into sacks of linen, and pressed in a vat 
filled with water: as long as any milky juice exudes 
the pressure is continued : the fluid gradually becomes 
clear, and a white powder subsides, which is starch. 

Starch is soluble in boiling water, but not in cold 
water, nor in spirits of wine. It is a characteristic 
property of starch to be rendered blue by iodine. 

Starch is more readily combustible than gum ; when 
thrown upon red-hot iron, it burns with a kind of ex- 
plosion, and scarcely any residuum remains. Accord- 
ing to MM. Gay Lussac and Thenard, 100 parts of 
starch are composed of. 

Carbon, with a small quantity of !.«.-- 

saline and earthy matter J 

Oxygen ... 49-68 

Hydrogen - - - 6*77 

Or, 
Carbon ... 43-55 

Oxygen and hydrogen in the^ 
proportions necessary to form V 56*46 
water . . J 

Supposing this estimation correct, starch may be con- 
ceived to be constituted by 15 proportions of carbon, 
13 of oxygen, and 26 of hydrc^en. 

Starch forms a principal part of a number of esculent 
vegetable substances. Sowans, cassava, salop, sago, all 
of them owe their nutritive powers principally to the 
starch they contain. 

Starch has been found in the following plants : — 
Burdock (Arctium Lappa\ Deadly Nightshade (Atro- 
pa Belladane), Bistort (Polygonum Bistorta)^ White 
Bryony (Bryonia aU>a)y Meadow Saffron (Colchicum 
autumnale)y Dropwort (Spircea Filipendula)^ Buttercup 
(Ranunculus bulbosus). Fig wort (Scrophularia nodosa)^ 



240 AGRICULTURAL CHEMISTRY. 

Dwarf Elder {Sambucus Auhu), Common Elder {Sam- 
bucus Nigra)y Foolstones {^Orchis Mario), Alezanden 
(Iniperatoria Ottruthium\ Herbane {Hyascyamus niger). 
Broad-leaved Dock {Rumex obtudfoUus\ Sharp-pointed 
Dock {Rumex acutu$)y Water Dock (Rumex eiquaticus). 
Wake Robin (Arum mactdatum\ Salep ( Orchis masculd). 
Flower de Luce, or Water-flag {Iris Pseudacorus), Stink- 
ing Gladwjn {Iris foetidissima), Eartbnut {Bunium But'- 



3. Sugar in its purest state is prepared from the ex- 
pressed juice of the Saccharum afficinarumj or sugar- 
cane : the acid in this juice is neutralized bj lime, and 
the sugar is crystallized by the evaporation of the aque- 
ous parts of the juice, and slow cooling : it is rendered 
white by the gradual filtration of water through it In 
the common process of manufacture, the whitening or 
refining of sugar is only effected in a great length of 
time ; the water being gradually suffered to percolate 
through a stratum of clay above the sugar. As the 
colouring matter of sugar is soluble in a saturated 
solution of sugar, or syrup, it appears that refining 
may be much more rapidly and economically performed 
by the action of syrup on coloured sugar.* The 
sensible properties of sugar are well known. Its spe- 
cific gravity according to Fahrenheit is about 1*6. It is 

* A French gentleman lately in this oonutry stated to the West Indk 
planters, that he was in possession of a very expeditious and eeooomical 
method of purifying and refining sugar, which he was willing to oom- 
municate to them for a very great pecuniary compensation. His terms 
were too high to he acceded to. Conversing on the subject with Sir 
Joseph Banks, I mentioned to him that I thought it probable that raw 
sugar might be easily purified bypassing syrup through it, which would 
dissolve the colouring matter. The same idea seems to have occurred 
about the same time, or before, to the late Edward Howard, Esq., who 
proved its efficacy experimentally, and some time before his death took 
out a patent for various improvements in the manuftctnre of sugar. 



LECTURE III. 241 

soluble in its own weight of water at 50^ ; it is likewise 
soluble in alcohol, but in smaller proportions. 

Lavoisier concluded from his experiments, that sugar 
consists in 100 parts of 

28 carbon, 

8 hydrogen, 
64 oxygen. 
Dr. Thompson considers 100 parts of sugar as com- 
posed of 27*5 carbon, 

7*8 hydrogen, 
64*7 oxygen. 
According to the recent experiments of Gay Lussac 
and Thenard, sugar consists of 42*47 of carbon, and 
57*53 of water or its elements. 

Lavoisier's and Dr. Thompson's analyses agree very 
nearly with the proportions of 

3 of carbon, 

4 of oxygen, 
and 8 of hydrogen. 

Gay Lussac's and Thenard's estimation gives the same 
elements as in gum ; 11 of carbon, 10 of oxygen, 20 of 
hydrogen. 

It appears from the experiments of Proust, Achaid, 
Goettling, and Parmentier, that there are many differ- 
ent species of sugar ready formed in the vegetable king- 
dom. The sugar of the American maple, Acer sacchor' 
rinum, is precisely the same as that of the cane. This 
sugar is used by the North American &rmers, who pro- 
cure it by a kind of domestic manufacture. The trunk 
of the tree is bored early in spring, to the depth of 
about two inches ; a wooden spout is introduced into 
the hole ; the juice flows for about five or six weeks. 
A common-isized tree, that is, a tree from two to three 
feet in diameter, will yield about 200 pints of sap, and 

VOL. vn. M 



242 AGRICULTURAL CHEMISTRY. 

every 40 pints of sap afford about a pound of sugar. 
The sap is neutralized by lime, and deposits crystals of 
sugar by evaporation. 

The sugar of grapes has been lately employed in 
France as a substitute for colonial sugar. It is procured 
from the juice of ripe grapes by evaporation and 
the action of pot-ashes.; it is less sweet Uian common 
sugar, and its taste is peculiar: it produces a sensation 
of cold while dissolving in the mouth ; and, it is proba- 
ble, contains a larger portion of water, or its elements. 

The roots of the beet (^Beta vulgaris and cicld) afford 
sugar by boiling, and the evaporation of the extract : it 
crystallizes and does not differ in its properties from the 
sugar of the cane in France. 

Manna, a substance which exudes from various trees, 
particularly from the Fraxinus QmuSj a i^cies of ash^ 
which grows abundantly in Sicily and Calabria, may 
be regarded as a variety of sugar very analagous to the 
sugar of grapes. A substance analagous to manna has 
been extracted by Fourcroy and Vauquelin from the 
juice of the common onion (AlUum Cepa), 

Besides the crystallised and solid sugars, there ap- 
pears to be a sugar which cannot be separated from 
water, and which exists only in a fluid form ; it consti- 
tutes a principal part of melasses or treacle ; and it is 
found in a. v^iety of fruits : it is more soluble in 
alcohol than solid sugar. 

The simplest mode of detecting sugar is that re- 
commended by Maigraaf. The vegetable is to be 
boiled in a small quantity of alcohol ; solid sugar, if 
any exist, will separate dioring the cooling of the solu- 
tion. 

Sugar has been extracted from the following v^eta- 
ble substances: 



LEGTUBB III. 243 

The sap of the Birch (Beiula (Ma), of the Sycar 
more (Acer Fseudaplatanua), of the Bamboo (Arundo 
Bambaa)^ of the Maize {Zeamaya), of the CowPanoip 
{Hercuileum SpandyUum), of the Coooa-nut tree {Cocos 
nucifera), of the Waloat-tiee {Jugiam alba), of the 
American aloes {Agave Americana), of the Dulse 
(Fttcus palmatus), of the Coimnon Panmip {Pbstanica 
sativcL), of St John's bread {Ceratmia SiUqua); the 
fruit of the common Arbutus {Arbutm Unedo), and 
other sweet-tasted fruits; the roots of the Turnip 
{Brassica Rapa), of the Carrot (Daucus Carota), of 
Parsley (Apium petroseUnum), the flower of the Euzine 
Rhododendron {Rhododendron poniicum), and firom the 
Dejptarium of most other flowers. 

The nutritive properties of sugar axe well known. 
At the time the British market was overnstocked with 
this article from the West India islands, pvoposala were 
made for applying it as the food of cattle ; experiments 
had been instituted, which proved that they might be 
&ttened by it : but difficulties connected with the 
duties laid on sugar prevented the plan from beiDg, 
tried to any extent. 

4. Albumen is a substance which has only lately 
been discovered in the vegetable kingdom. It.abounds 
in the juice of the Papaw-;tree (Cariea papaya:) when 
the juice is boiled» the albumen falls down in a coagu- 
lated state. It is likewise found . in . mushrooms, and in 
different ^cies of fungusea 

Albumen, in its pure form, is a thick, glahy, tasteless 
fluid ; precisely the same as the white; of die egg; it is 
soluble in cold water; its sobitLgn^ when not too 
diluted, is coagulated by boilinjD^ and the albumen 
separates in the fcmn of thin flakes. Albumen, is like- 
wise coagulated by acids and by akohol : a solution of 

m2 



244 AORICULTUIULL CHEKISTRY. 

albumen giyes a precipitate when mixed with a cold 
solution of nutgalls. Albtftnen, when burnt, produces 
a smell of volatile alkali, and affords carbonic add and 
water ; it is therefore evidently principally composed of 
carbon, hydrogen, oxygen, and azote. 

AcconUng to the experiments of Gay Lussac and 
Thenard, 100 parts of albumen from the white of the 
e^ are composed of 

Carbon - - 52-883 

Oxygen - - 23872 

Hydrogen - - 7-540 

Azote - - 15-705 

This estimation would authorise the supposition that 
albumen is composed of 2 proportions of azote, 5 oxy- 
gen, 9 carbon, 32 hydrogen. 

The principal part of the almond, and of the kernels of 
many other nuts, appears from the experiments of Proust 
to be a substance analogous to coagulated albumen. 

The juice of the fruit of the Ochra (JBSbiscus eseu- 
lentuSi) according to Dr. Clarke, contains a liquid 
albumen in such quantities, that it is employed in 
Dominica as a substitute for the white of eggs in 
clarifying the juice of the sugar-cane. 

Albumen may be distinguished from other substances 
by its property of coagulating by the action of heat or 
acids, when dissolved in water. According to Dr. 
Bostock, when the solution contains only one grain of 
albumen to 1000 graios of water, it becomes cloudy by 
being heated. 

Albumen is a substance common to the animal as 
well as to the vegetable kingdom, and much more 
abundant in the former. 

5. Gluten may be . obtained from wheaten flour by 
the following process : — the flour is to be made into a 



LECTURB III. 245 

paste, which is to be caudoosly washed, by kneading 
it under a small stream of water, till the water has 
carried off from it all the starch; what remains is 
gluten. It is a tenacious, ductile, elastic substance. 
It has no taste. By exposure to air, it becomes of a 
brown colour. It is very slightly soluble in cold water ; 
but not soluble in alcohoL When a solution of it in 
water is heated, the gluten separates in the form of 
yellow flakes ; in this respect it agrees with albumen, 
but differs from it in being infinitely less soluble in 
water. The solution of albumen does not coagulate 
when it contains much less than 1000 parts of albumen ; 
but it appears that gluten requires more than 1000 
parts of cold water for its solution. 

Gluten, when burnt, affords similar products to 
albumen, and probably differs very little fix>m it in 
composition. Gluten is found in a great number of 
plants: Proust discovered it in acorns, chesnuts, horse- 
chesnuts, apples and quinces ; barley, lye, peas, and 
beans ; likewise in the leaves of rue, cabbage, cresses, 
hemlock, borage, safiron, in the berries of the elder, 
and in the grape. Gluten appears to be one of the 
most nutritive of the vegetable substances ; and wheat 
seems to owe its superiority to other grain from the 
circumstance of its containing it in larger quantities. 

6. Gum elastie or Ccumtchouc is procured from the 
juice of a tree which grows in the Brazils, called Hsevea. 

' When the tree is punctured, a milky juice exudes 
from it, which gradually deposits a solid substance ; and 
this is g^m elastic. 

* Gum elastic is pliable and soft like leather, and 
becomes softer when heated. In its pure state it is 
white ; its specific gravity is 9335. It is combustible, 
and bums with a white flame, throwing off a dense 



246 AORICnLTURAL CHBMISTRT. 

smoke^ with a TCfy disagieeable amelL It is infloInUe 
in water and in alcohol ; it is sokiUe in ether» YokitOe 
oUb, and in petroleum, and may be procured firom 
ether in an unaltered state by eraporating its solution 
in that liquid. Gum elastic seems to exist in a great 
varie^ of plants : amongst them are, Jatropha ebuHea, 
Ficiu indieOf Ar^Korptu integrifMoy and Uroeola eUu- 
tiea, 

Bifd^lime, a sdMance which may be procured from 
the holly, is rery sBsalogoqs to gum elastic in its pro- 
perties. Species of gum elastic may be obtained from 
the misletoe, from gum-mastic, opium, and from the 
berries of the SmUax eaduca, in which last plant it has 
been lately discoyered by Dr. Barton. 

Gum elastic, when distilled, aflfbrds Ti^tile alkali, 
water, hydrogen, and carbon, in different combinations. 
It therefore consists principally of asote^ hydrogen, 
oxygen, and carbon; but the proportions in which 
they are combined have not yet been ascertained. 
Grmn elastic is an indigestible substance, not fitted 
iat the food of snimah ; its uses in the arts are well 
known. 

7. JExtract or the extraetive principle^ exists in almost 
all plants. It may be procured in a state of tolerable 
purity from safiron, by merely infusing it in water, and 
evaporating the solution. It may likewise be obtained 
from catechu, or Terra japtmea, a substance brought 
from India. This substance consists principally of 
asldngent matter, and extract; by the action of water 
upon it, the astringent matter is first dissolved^ and may 
be sepaiBted from the extract.' Extract is always more 
or less coloured : it is soluble in alcohol and water, but 
not soluble in ether. It unites with alumina, when 
that earth is boiled in a solution of extract ; and it 



LECrURB III. 247 

is precipitated by the salts of alumina^ and by many 
metidlic solutions, particularly the solution of muriate 
of tin. 

From the products of its distillation, it seems to be 
composed principally of hydrogen, oxygen, carbon, and 
a little azotCk 

There appears to be almost as many varieties of 
extract as there are species of plants. The difference 
of their j^operties probably in many cases depends 
upon their being combined with small quantities of 
other vegetable principles, or to their containing dif- 
ferent saline, alkaline, acid, or earthy ingredients. 
Many dyeing substances seem to be of the nature of 
extractive principle ; such as the red colouring matter 
of madder, and the yellow dye procured from weld. 

Extract has a strong attraction for the fibres of cotton 
or linen, and combines with these substances when 
they are b<»led in a solution of it. The combination is 
made stronger by the interventicm of mordants, which 
are earthy or metallic combinations that unite to the 
cloth, and enable the colouring matter to adhere more 
strongly to its fibres. 

Extract, in its pure form, cannot be used as an 
article of food; but it is probably nutritive when 
united to starch, mucilage, or sugar. 

8. Tanittn, or the tanning principle, may be pro- 
cured by the action of a small quantity of cold water 
on bruised grape-seeds, or pounded gall-nuts; and 
by the evaporation of the solution to dryness. It ap- 
peals as a yellow substance, posslsssed of a highly 
astringent taste. It is difficult of combustion. It 
is very soluble, both in water and alcohol, but insoluble 
in ether. When a solution of glue, or isinglass {gela- 
tine,) is mixed with an aqueous solution of tannin, 



248 AGRICULTURAL CHBHI8TRY. 

the two substances, t. e. the animal and vegetable 
mattefSy fall down in oombinationj and fonn an insoluble 
precipitate. 

When tannin is distilled in close vessels, the prin- 
cipal products are charcoal, carbonic acid, and inflam- 
mable gases, with a minute quantity of volatile alkalL 
Hence its elements seem the same as those of extract, 
but probably in different proportions. The charac- 
teristic property of tannin is its action upon solutions <^ 
isinglass or jelly ; this particularly distinguishes it fiom 
extract, with which it agrees in most other chemical 
qualities. 

There are many varieties of tannin, which probably 
owe the difference of their properties to combinations 
with other principles, especially extract, fix>m which 
it is not easy to free tannin. The purest species of 
tannin is that obtained from the seeds of the grape; 
this forms a white precipitate, with solution of isin- 
glass. The tannin from gall-nuts resembles it in its 
properties. That from sumach affords a yellow precipi- 
tate, that from kino a rose-coloured, that from catechu 
a fawn-coloured one. The colouring matter of Brazil 
wood, which M. Chevreul considers as a peculiar 
principle, and which he has called Hematine, differs 
from other species of tannin, in affording a precipitate 
with gelatine, which is soluble in abundance of hot 
water. Its taste is much sweeter than that of the other 
varieties of tannin, and it may perhaps be regarded as 
a substance intermediate between tannin and extract. 

Tannin is not a nutritive substance, but it is of great 
importance in its application to the art of tanning. 
Skin consists almost entirely of jelly or gelatine, in 
an organized state, and is soluble by the long-continued 
action of boiling water. When skin is exposed to 



LECTURE III. 249 

solutions containiBg taimiii, it siowlj combines with 
that principle ; its fibrous texture and coherence are 
preserved ; it is rendered perfectly insoluble in water, 
and it is no longer liable to putrefaction: in short, 
it becomes a substance in chemical composition pre- 
cisely analogous to that fumi^ed by the solution of 
jelly and the solution of tannin. 

Li general, in this country, the bark of the oak 
18 used for affording tannin in the manu&cture of 
leather : but the barks of some other trees, particularly 
the Spanish chesnut, have lately come into use. The 
following table will give a general idea of the relative 
value of different species of barks. It is founded on 
the result of experiments made by myself. 

Table qf Numben exktbiiing the quanHiy of Tannin afforded by 480{6#. 
of different Barki, which exprets nearly their relaHoe Valuee. 



Ayerage of entire Bark of middle-Blzed Oak, cut in spring - 
of Spanish Chesnat ... 
... .. of Leicester Willow, large size 

..• - .. of Elm . - . - . 

of Common Willow, large 
... ... of Ash ..... 

.. • .. of Beech - - - . - 

of Horse Chesnut ... 

of Sycamore - . . - 

of Lbmbardy Poplar . . - 
of Birch . . . . - 

of Hazel . . . - - 
of Black Thorn .... 

of Coppice Oak - . - 
of Oak, cut in autumn ... 
of Larch, cut in autumn 
White interior cortical layers of Oak Bark - . . 



lb. 
29 

di 

33 
13 
11 
16 
10 

9 
11 
16 

8 
14 
16 
32 
21 

8 
72 



The quantity of the tannin principle in barks differs 
in different seasons; when the spring has been very 
cold the quantity is smallest. On an average^ 4 or 5 
lbs. of good oak bark are required to form 1 lb. of 
leather. The inner cortical layers in all barks contain 

M 5 



250 AGRICULTUBAIi CHEMISTRY. 

the laigefit quantity of tannin. Baiks contain the 
greatest proportion of tannin at the time the buds be^^ 
to open — the smallest quantity in winter. 

The extractive or colouring matters found in barks, 
or in substances- used in tanning, influence the quality 
of leather. Thus skin tanned with gall-^nuts is much 
paler than skin tanned with oak bark, which contains a 
brown extractive matter. Leather made firom catechu 
is of a reddish tint It is probable that in the process 
of tannings the matter of skin and the tanning prin- 
ciple first enter into union, and that the leather, at 
the moment of its fbrmatioD, unites to the extractive 
matter* 

In general, skins in being converted into leather in- 
crease in weight about one-third ; * and the operation 
is most perfect when they are tanned slowly. When 
skins are introduced into very strong infusions of tannin, 
the exterior parts immediately combine with that prin- 
ciple, and defend the interior parts from the action of 
the solution : such leather is liable to crack and to decay 
by the action of water. 

The precipitates obtained from infusions containing 
tannin by isinglass, when dried, contain at a medium 
rate about 40 per cent of vegetable matter. It is easy 
to obtain the comparative value of different substances 
for the use of the tanner, by comparing the quantities 
of precipitate afforded by infusions of given weights 
mixed with solutions of glue or isinglass. 

To make experiments of this kind, an ounce, or 180 
grains of the vegetable substanee, in coarse powder, 
^ould be acted upon by half a pint of boiling wat^. 
The mixture should be frequently stirred, and suffered 

* This estimafloa must be conBidered as applying to drp skin and 
dryleatlier. 



LECTUBB in. 251 

to stand twenty-foar hours; the flaid should then be 
passed through a fine linen cloth, and miled with an 
equal quakitity of solution of gelatine, made by dis- 
solving glue, jelly, or isinglass in hot water, in the pro- 
portion of a drachm of glue or isinglass, or six table- 
spoonfuls of jelly, to a pint of water. The precipitate 
should be collected by passing the mixture of the solu- 
tion atid infusion through folds of blotting-paper, and 
the paper exposed to the air till its contents are quite 
dry. If pieces of paper of equal weights are used, in 
cases in which different vegetable substances are em- 
ployed, the difference of the weights of the papers, 
when dried, vnll indicate with tolerable accuracy the 
quantities of tannin contained by the substances, and 
their relative value, for the purposes of manu&ctute. 
Foup-tenths of the increase of weight, in grains, must 
be taken, which will be in relation to the weights in the 
table. 

Besides the barks already mentioned, there are a 
number of others which contain the tanning principle. 
Few barks, indeed, are entirely free from it It is 
likewise feund in the wood and leaves of a number of 
trees and shrubs, and is one of the most generally dif- 
fused of the vegetable principles. 

A stibstance very similar to tannin has been formed 
by Ml*. Hatchett, by the action of heated diluted nitric 
acid on charcoal, and evaporation of the mixture to 
dryness. From 100 grains of charcoal Mr. Hatchett 
obtained 120 grains of artificial tannin, which, like 
natural tannin, possessed the property of rendering skin 
in^luble in water. 

Both natural and artificial tannin form compounds 
with the alkalies and the alkaline earths; and these 
compounds are not decomposable by skin. The attempts 



252 AQRICUtTURAL CHEMISTRY. 

that have been made to render oak bark more effi- 
cient as a tanning material by infusion in lime water, 
are consequently founded on erroneous principles. 
Lime forms with tannin a compound not soluble in 
water. 

: The acids unite to tannin, and produce com- 
pounds that are more or less soluble in water. It 
is probable that in some y^;etable substances tamiin 
exists combined with alkaline or earthy matter; 
and such substances will be rendered more effica- 
cious for the use of the tanner by the action of diluted 
acids. 

9. Indigo may be procured from woad {Isotu tme- 
toria)y by digesting alcohol on it, and evaporating the 
solution. White crystalline grains are obtained, which 
gradually become blue by the action of the atmosphere : 
these grains are the substance in question. 

The indigo of commerce is principally brought from 
America. It is procured from the Indigofera aryentea, 
or wild indigo, the Indigofera dupermoj or Gnatimala 
indigo, and the Indigofera tindoria, or French indigo. 
It is prepared by fermenting the leaves of those trees 
in water. Indigo, in its coomion form, appears as a 
fine deep blue powder. It is insoluble in water, and 
but slightly soluble in alcohol : its true solvent is sul- 
phuric acid : 8 parts of sulphuric acid dissolve 1 part 
of indigo ; and the solution diluted with water forms a 
very fine blue dye. 

' Lidigo, by its distillation, a£Pords carbonic add gas, 
water, charcoal, ammonia, and some oily and acid mat- 
ter ; the charcoal is in very lai^e propoxtion. Pure in- 
digo, therefore, most probably consists of carbon, hydro- 
gen, oxygen, and azote. 
L . Indigo owes its blue colour to combination with oxy- 



LBCTURE III. 253 

gen. For the uses of the dyers, it is partly deprived of 
oxygen, by digesting it with orpiment and lime water, 
when it becomes soluble in the lime water, and of a 
greenish colour. Cloths steeped in this solution com- 
bine with the indigo ; they are green when taken out 
of the liquor, but become blue by absorbing oxygen 
when exposed to air. 

Indigo is one of the most valuable and most exten- 
sively used of the dyeing materials. 

10. There are a number of colouring principles found 
in different vegetable productions, the properties of 
which are less marked than those of indigo, and the se- 
paration more difficult. The colouring matters of car- 
thamus and madder are the most fixed amongst the red 
vegetable colours. A number of vegetable substances 
are rendered red by the action of acids, and green by 
that of alkalies. They all seem to be composed of dif- 
ferent proportions of hydrogen, oxygen, and carbon; 
but are so liable to change, that few distinct experiments 
have been made upon their nature. In dyeing, they 
are usually applied to cloths prepared for receiving them 
by combination with certain saline or metallic prepara- 
tions called mordants ; and, in consequence of the triple 
union formed between the cloth, the mordant, and the 
colouring matter, the tint is modified, or changed, and 
rendered more permanent 

11. The hitter principle is very extensively difiused in 
the v^;etable kingdom ; it is found abundantly in the 
hop {Humtdus lupultu), in the common Broom {Spar- 
Hum scaparium), in the Chamomile (Anthemis nobilis), and 
in Quassia amara and exceha. It is obtained from those 
substances by the action of water or alcohol, and eva- 
poration. It is usually of a pale yellow colour; its taste 
is intensely bitter. It is very soluble, both in water 



254 AOBICXTLTITBAL CHEMISTRY. 

and alcohol; and has little or no action on alkaline, 
acid> saline, or metallic solutions. 

An artificial substance, similar to the bitter principle, 
has been obtained by digesting diluted nitric acid on 
silk, indigo, and the wood of the white willow. This 
substance has the property of dyeing cloth of a bright 
yellow colour ; it differs from the natural bitter prin- 
ciple in its power of combining with the alkalies ; in 
union with the fixed alkalies, it constitutes crystallised 
bodies, which have the property of detonating by heat 
or percussion* 

The natural bitter principle is of great importance 
in the art of brewing; it checks fennentation, and 
preserves fermented liquors; it is likewise used in 
medicine. 

The bitter principle, like the narcotic principle, ap- 
pears to consist principally of carbon, hydrogen, and 
oxygen, with a little azote. 

12. Wax is found in a number of vegetables ; it is 
procured in abundance from the hemes of the Wax 
Myrtle (Myrica ceriferd) ; it may be likewise obtained 
from the leaves of many trees, in its pure state it is 
white. Its specific gravity is «9662, it melts at 155 
degrees; it is dissolved by boiling alcohol; but it is 
not acted upon by cold alcohol ; it is insoluble in wa- 
ter: its properties, as a combustible body, are well 
known. 

The wax of the vegetable kingdom seems to be pre- 
cise^ of the same nature as that afforded by the bee. 

From the experiments of MM. Gay Lussac and 
Thenard, it appears that 100 parts of wax consist of 
Carbon .... 1-784 

Oxygen .... 6*544 

Hydrogen .... 12-672 



LECTURE III. 255 

Or of 



Carbon - - . - 81-784 

Oxygen and hydrogen in the "j 

proportions necessary to > 6*300 
form water - - J 
Hydrogen - - - - 11'916 
Which agrees very nearly with 37 proportions of hydro- 
gen, 21 of charcoal^ 1 of oxygen. 

13. Besin is very common in the vegetable king- 
dom. One of the most usual species is that afforded 
by the different kinds of fir. When a portion of the 
bark is removed firom the fir-tree in spring, a mat- 
ter exudes, which is called turpentine; by heating 
this turpentine gently, a volatile oil rises firom it, 
and a more fixed substance remains : this substance is 
resin. 

The resin of the fir is the substance commonly known 
by the name of rosin ; its properties are well known. 
Its specific gravity is 1072. It melts readily, bums with 
a yellow light, throwing off much smoke. Resin is 
insoluble in water, either hot or cold; but very soluble 
in alcohol. When a solution of resin in alcohol is 
mixed with water, the solution becomes milky; the 
resin is deposited by the stronger attraction of the 
water for the alcohol. 

Resins are obtained firom many other species of trees. 
Masdch firom the PUtada lerUiscus, Elemi firom the 
Amyris elemferay Copal firom the Khu copalUninn, 
Sandarach finom the common juniper. Of these resins 
copal is the most peculiar. It is the most difiicultly 
dissolved in alcohol; and for this purpose must be 
exposed to that substance in vapour; or the alcohol 
employed must hold camphor in solution. According 
to Gay Lussac and Themard, 



256 AQRICUtTURAL CHEMISTRY. 



100 parts of common resin contain 






Carbon - - - - 


75-944 




Oxygen .... 
Hydrogen - - - - 
Or of 


13-337 
10-719 




Carbon . - - - 


75-944 




Oxygen and hydrogen in the^ 
proportions necessary to > 
form water - - J 


15-166 




Hydrc^n in excess - - 8*900 
According to the same chemists, 100 parts of 
consist of 


copal 


Carbon . . . - 


76-811 




Oxygen .... 
Hydrogen - . - - 


10-606 
12-583 





Or, 

Carbon .... 76-11 
Water or its elements - - 12-052 
Hydrogen .... 11 -137 

From these results, if resin be a definite compound, 
it may be supposed to consist of 8 proportions of 
carbon, 12 of hydrc^en, and 1 of oxygen. 

Resins are used for a variety of purposes. Tar and 
pitch principally consist of resin, in a partially decom- 
posed state. Tar is made by the slow combustion of 
the fir ; and pitch by the evaporation of the more volatile 
parts of tar. Resins are employed as varnishes, and 
for these purposes are dissolved in alcohol or oils. 
Copal forms one of the finest It may be made by 
boiling it in powder with oil of rosemary, and then 
adding alcohol to the solution. 

14, Camphor is produced by distilling the wood of 
the Camphor-tree (Laurus camphara), which grows in 
Japan. It is a veiy volatile body, and may be purified 



LECTURE III. 257 

by distillation. Camphor is a white, brittle^ semitrans- 
parent substance, having a peculiar odour, and a strong 
aciid taste. It is very slightly soluble in water ; more 
than 100,000 parts of water are required to dissolve 1 
part of camphor. It is veiy soluble in alcohol ; and by 
adding water in small quantities at a time to the solution 
of camphor in alcohol, the camphor separates in a crys- 
tallised form. It is soluble in nitric acid, and is sepa^ 
rated from it by water. 

Camphor is very inflammable ; it bums with a bright 
flame, and throws off a great quantity of carbonaceous 
matter. It forms, in combustion, water, carbonic acid, 
and a peculiar acid called camphoric acid. No accu- 
rate analysis has been made of camphor, but it seems 
to approach to the resins in its composition ; and con- 
sists of carbon, hydrogen, and oxygen. 

Camphor exists in other plants besides the Laurus 
camphorcu It is procured from species of the Laurus 
growing in Sumatra, Borneo, and other of the East 
Indian isles. It has been obtained from Thyme {Thy- 
mus serpyllum^ Marjoram {Origanum mqjoranay) Ginger 
tree (Amomum zingiber). Sage {Salvia officinalis). Many 
volatile oils yield camphor by being merely exposed to 
the air. 

An artificial substance very similar to camphor has 
been formed by M. Kind, by saturating oil of turpen- 
tine with muriatic acid gas (the gaseous substance pro- 
cured from common salt by the action of sulphuric 
acid.) The camphor procured in well-conducted ex- 
periments amounts to half of the oil of turpentine 
used. It agrees with common camphor in most of its 
sensible properties ; but differs materially in its chemi- 
cal qualities and composition. It is not soluble without 
decomposition in nitric acid. From the experiments of 



258 AGRICULTURAL CHEMISTRY. 

Gehlen^ it appears to consist of the elements of oil of 
turpentine^ carbon, hydrogen, and oxygen, united to 
the elements of muriatic gas, chlorine and hydrogen. 

From the analt^ of artificial to natural camphor, it 
does not appear improbable that natural camphor may be 
a secondary vegetable compound, consisting of cam- 
phoric acid and volatile oiL Camphor is used medi- 
cinally, but it has no other application. 

15. Fixed oil is obtained by expression ftom seeds 
and fruits; the olive, the almond, linseed, and rapeseed, 
afford the most common vegetable fixed oils. The 
properties of fixed oils are well knovm. T\mi specific 
gravity is less than that of water; that of olive and of 
rape-seed oil is *913; that of linseed and almond oil 
*932 ; that of palm oil '968 ; that of walnut and beech- 
mast oil '923. Many of the fixed oik congeal at a 
lower temperature than that at which water fif^ezes. 
They all require for their evaporation a higher tem- 
perature than that at which water boils. The pro- 
ducts of the combustion of oil are water and carbonic 
acid gas. 

From the experiments of Gay Lussac and Thenard, 
it appears that olive oil contains, in 100 parts. 

Carbon ... 77-213 

Oxygen ... 9-427 

Hydrogen - • . 13360 

This estimation is a near approximation to 1 1 pro- 
portions of carbon, 20 hydrogen, and 1 oxygen. 

The following is a list of fixed oils, and of the trees 
that afford them. 

Olive oil, firom the Olive tree (^Olea europed)^ Linseed 
oil, firom the common and perennial Flax {TJnum usiioi^ 
tissimum etperenne)^ Nut oil^ firom the Hazel nut {Cary^ 



LECTURE UI. 259 

lus AveUana), Walnut {Jvglans regid)y Hemp oil, fiom 
the Hemp {Cannabis sativa)^ Ahmmd oil, from the sweet 
Almond {Amygdalus communis)^ Beech oil^ from the 
common Beech {Fagm sylvatica)^ Rape-seed oil, from 
the Rapes (Brassica Napus et campestris), Poppy oil, 
from the Poppy (Papaver somniferum), oil of Sesamum, 
fit)m the Sesamum {Sesamum orientale). Cucumber oil, 
from the gourds {Cucurbita Pepo et Mehpepo)^ oil of 
Mustard, from the Mustard {Sinapis nigra et arvensis)y 
oil of Sunflower, from the annual and perennial Sun- 
flower {Helianthtis annutts et perennis). Castor oil, from 
the Palma Christi {Ridnus communis^ Tobacco-seed 
oil, from the Tobacco {Nicotiana Tabacum et rusticd). 
Plum kernel oil from the Plum tree (Pruntis domestica). 
Grape-seed oil, from the Vine ( ViHs vinifera). Butter of 
cacoa, from the Cacoa tree ( Theobroma Cacao)^ Laurel 
oil, from the sweet Bay tree {Lauras nobiUs). 

Hie fixed oils are very nutritive substances: they 
are of great importance in their applications to the 
purposes of life. Fixed oil, in combination with soda, 
forms the finest kind of hard soap. The fixed oils are 
used extensively in the mechanical arts, and for the 
preparation of pigments and varnishes. 

16. Volatile oil, likewise called essential oil, difiers 
firom fixed oil, in being capable of evaporation by a 
much lower degree of heat, in being soluble in alcohol, 
and in possessing a very slight degree of solubility in 
water. 

There is a great number of volatile oils, distinguished 
by their smell, their taste, their specific gravity, and 
other sensible qualities. A strong and peculiar odour 
may, however, be considered as the great characteristic 
of each species : the volatile oils inflame with more 
fiicility than the fixed oils, and afford, by their com^ 



260 AGRICULTURAL CHEMISTRY. 

bastion^ different proportions of the same sabstances^ 
water^ carbonic acid, and carbon. 

The following specific gravities of different volatile 
oils were ascertained by Dr. Lewis: — 



Oil of Sassafiras 1094 


Oil of Tansy 


946 


Cinnamon 1035 


Caraway 


940 


Cloves 1034 


Origanum 


940 


Fennel 997 


Spike 


936 


DiU 994 


Rosemary 


934 


Penny Royal 978 


Juniper 


911 


Cumin 975 


Oranges 


888 


Mint 975 


Turpentine 


792 


Nutmegs 948 







The peculiar odours of plants seem, in almost all 
all cases, to depend upon the peculiar volatile oils they 
contain. All the perfiimed distilled waters owe their 
peculiar properties to the volatile oils they hold in solu- 
tion. By collecting the aromatic oils, the firagrance of 
flowers, so fiigitive in the common course of nature, is 
as it were embodied and made permanent 

It cannot be doubted that the volatile oils consist of 
carbon, hydrc^n, and oxygen ; but no accurate experi- 
ments have as yet been made on the proportions in 
which these elements are combined. 

The volatile oils have never been used as articles of 
food ; many of them are employed in the arts, in the 
manufiM^ture of pigments and varnishes ; but their most 
extensive application is as perfumes. 

17* Woody fbrt is procured fix>m wood, bark, leaves 
or flowers of trees, by exposing them to the repeated 
action of boiling water and boiling alcohoL It is the 
insoluble matter that remains, and is the basis of the 
solid organized parts of plants. There are as many 



LECTURE III. 261 

varieties of woody fibre as there are plants and organs 
of plants ; but they are all distinguished by their fibrous 
texture, and their insolubility. 

Woody fibre bums with a yellow flame, and produces 
water and carbonic acid in burning. When it is dis- 
tilled in close vessels, it yields a considerable residuum 
of charcoal. It is from woody fibre, indeed, that char- 
coal is procured for the purposes of life. 

The following table contains the results of experi- 
ments made by Mr. Mushet, on the quantity of charcoal 
afforded by different wood : — 

100 parts of Lignum Vitae - - 26*8 of charcoal 

Mahogany - - 25*4 

„ Laburnum - - 24*5 

Chesnut ... 23*2 

Oak - - - - 22-6 

American black Beech - 21*4 

Wahiut ... 20.6 

HoUy- - - - 19-9 

Beech ... 19*9 

■ American Maple - 19*9 

Elm .... 19-5 

Norway Pine - - 19*2 

Sallow ... 18*4 

Ash ... - 17-9 

Birch .... 17-4 

Scottish Fir - - 16-4 

MM. Gay Lussac and Thenard have concluded firom 
their experiments on the wood of the oak and the beech, 
that 100 parts of the first contfun :— 

Of Carbon . . - - 52-53 

— Oxygen . - - - 41-78 

— Hydrogen ... 6'69 



262 AGRICULTURAL CHBMISTBY. 

and 100 parts of the seGond : — 

Of Carbon - - - - 51-45 

— Oxygen - - - - 4ffi-73 

— Hydrogen . . - 6-82 
Suj^osbg woody fibre to be a definitive compoiuidy 

these estimations lead to the conclusion, that it oonsasta 
of 5 proportions of carbon, 3 of oxygen, and 6 of hy- 
drogen ; or 57 carbon, 45 oxygen, and 6 hydrc^n. 

It will be unnecessary to speak of the api^ications of 
woody fibre. The different uses of the woods, cotton, 
linen, the barks of trees, are sufficiently known. Woody 
fibre appears to be an indigestible substance. 

18. The acids found in the vegetable kingdom are 
numerous ; the true vegetable acids which exist ready 
formed in the juices or organs of plants, are the axaHe^ 
citric, tartaric, benzoic, acetic, mecanic, malic, galUc, and 
prussic acid. 

All these acids, except the acetic, malic» and prussic 
acids, are white crystallized bodies. The acetic, malic, 
and prussic acids, have been obtained only in the fluid 
state ; they are all more or less soluble in water : all have 
a sour taste, except the gallic and prussic acids; of 
which the first has an astringent taste, and the latter a 
taste like that of bitter almonds. The meconic acid 
exists in opium. 

The oxalic acid exists, uncombined, in the liquet 
which exudes firom the Chich pea (Ctcer arietinum), and 
may be procured firom wood Sorrel (OxaUs AcetoseUa), 
common sorrel, and other species of Bumex ; and 6rom 
the Geranium acidum. Oxalic acid is easily discovered 
and distinguished firom other acids, by its property of 
decomposing all calcareous salts, and forming with lime 
a salt insoluble in water ; and by its crystallizing in four^ 
sided prisms. 



LECTURE ni. 263 

The citric acid is the peculiar acid existing in the 
juice of lemons and oranges. It may likewise be ob- 
tained from the crtmherrjy whortlebeny, and hip. 

Citric acid is distinguished by its forming a salt inso- 
luble in water with lime; but decomposable by the 
mineral acids. 

The tartaric add may be obtained from the juice of 
mulberries a2id grapes; and likewise from the pud^ of 
the tamarind* It is characterized by its i»*opeyty of 
foaning a difficultly-soluble salt with potassa, and an inso- 
luble salt decomposable by the mineral adds with lime^ 

Bepzoic add may be procured tcosa several ledinouft 
substances by distillation : from benxoioi, sfonCz^ -and 
balsam of Tc^u. It is distisguished from the other acids 
by its anmiatic odour^ and by ils extreme volatility. • 

Malic add may be. obtained from the juice of apples^ 
barberries,, plums, elderberries, currants, strawbenies,* 
and raspberries. . It forms a sdkiUe sak with lime; and 
is eadly distinguished bythis tss^ from the adds already 
named. 

Acetic add, or vinegar, may be obtained from the sap 
of different trees. It is distiibtguisfaed from malie acid^ by 
its peculiar odour ; and from ithe other Tegetable acids, 
by forming soluble salts with tiie alkalies aikl earths. 

Gallic add may be obtained, by gently and gp»dually 
heating powdered gall-nuts, and receiving the volatSe- 
matter in a cool vesseL A number <tf white crystals 
win. appear, which are.. distinguished by their property 
of rendering solutions of iroo; deep pusple. 

The vegetable prussic acid, is procured by distilling 
laurel leaves^ or the kernels of the peach, and chevry, or 
bitter aknonds. it is characterized by its property of 
forming a bluish-green precipitate, wlieir a litde alkali 
is added to it, and it is poured into sohitions containing 



264 AGRICULTURAL CHEMISTRY. 

iron. It is very analogous in its properties to the pnis- 
sic acid obtained from animal substances ; or by passing 
ammonia over heated charcoal : but this last body fomu^ 
with the red oxide of iron, the deep bright blue sab- 
stance called Prussian blue. 

Some other vegetable acids have been found in the 
products of plants ; the morolyxic acid in a saline exu- 
dation from the white mulberry tree, and the kinic add 
in a salt afforded by Peruvian bark; but these two 
bodies have as yet been discovered in no other cases. 
The igasuric add is so named by its discoverers, MM. 
Pelletier and Caventou : and the boletic, nanceic, fun- 
g^c, and ellagic adds, have been described by M. Bra- 
connot; but their properties are too little interesting to 
the agriculturist, to insert a description in this place. 
The phosphoric add is found free in the onion ; and 
the phosphoric, sulphuric, muriatic, and nitric adds, 
exist in many saline compounds in the vegetable 
kingdom ; but they cannot with propriety be considered 
as vegetable products. Other acids are produced during 
the combustion of vegetable compounds, or by the action 
of nitric acid upon them ; they are the camphoric add, 
the mucous or saclactic acid, and the suberic add; the 
first of which is procured from camphor ; the second 
from gum or mucilage ; and the third from cork, by the 
action of nitric acid. 

From the experiments that have been made upon 
the vegetable adds, it appears that all of them, except 
the prussic add, are constituted by different proportions 
of carbon, hydrogen, and oxygen: the prussic add 
consists of carbon, azote, and hydrogen, with a little 
oxygen. The gallic acid contains more carbon than 
any of the other vegetable acids. 

The following estimates of the composition of some 



LECTUBE III. 



265 



of the vegetable acids have been made by Gay Lussac 

andThenard: — 

100 parts of oxalic acid contain : 

Carbon - - 26-566 

Hydn^n - - 2745 

Oxygen - - 70689 

100 parts of tartaric acid contain : 

Carbon - - 24-050 

Hydrogen - - 6*629 

Oxygen - - 69-321 

Ditto citric acid: 

Carbon - - 33-811 

Hydrogen - - 6-330 

Oxygen - - 59859 

100 parts of acetic acid : 

Carbon - - 50*224 

Hydrogen - - 5-629 

Oxygen - - 44-147 

Ditto mucous or saclactic acid : 

Carbon - - 33-69 

Hydn^en - - 3-62 

Oxygen - - 62-69 

These estimations agree nearly with the following 

definite proportions. In oxalic acid, 7 proportions of 

carbon, 8 of hydrogen, and 15 oxygen, ; in tartaric 

acid, 8 carbon, 28 hydrogen, 18 oxygen; in citric 

acid, 3 carbon, 6 hydrogen, 4 oxygen ; in acetic acid, 

18 carbon, 22 hydrogen, 12 oxygen ; in mucous acid, 

6 carbon, 7 hydrogen, 8 oxygen. 

The applications of the vegetable adds are well 
known. The acetic and citric acids are extensively 
used. The agreeable taste and wholesomeness of 
various vegetable substances used as food materially 
depend upon the vegetable acid they contain. 
VOL. vn. N 



266 AGRICULTURAL CHEMISTRY. 

19. It is uncertain whether ammonia or the volatile 
alkali exists ready formed in plants : but it is evolved 
rom many of them by the action of lime or fixed 
alkali^ assisted by a gentle heat; though it may be 
always imagined to be generated during the process by 
the combination of azote and carbon. The ingenious 
researches of M. Sertumer^ followed by those of other 
chemists, have made us acquainted with the alkaline 
properties of several compound vegetable substances, 
which were not suspected to belong to this class of 
bodies, such as morphina, strychnina, brucina, picro- 
toxina, delphina; these compounds, which are found 
respectively in opium, nux vomica, Bruoea antidy- 
senterica, cocculus indicus, and Delphinium Staphi- 
sagria, agree with alkalies in their effects upon vegetable 
colours, and in combining with acids, into peculiar 
neutro-saline compounds. They form the narcotic or 
poisonous principles of the plants in which they are 
found, and probably many more of them will be dis- 
covered. They are not very interesting to the agri- 
culturist, except in this point of view, that possUdy 
many noxious vegetable stibstances may be rendered usefnl 
as the food of cattle, by extracting their noxious principles 
by means of acids ; and this is a subject well worthy of 
experimental investigation. 

JFixed alkali may be obtained in aqueous solution 
fi'om most plants by burning them, and treating the 
ashes with quick-lime and water. The vegetable alkaU, 
or potassa, is the common alkali in the vegetable king- 
dom. This substance, in its pure state, is white and 
semi-transparent, requiring a strong heat for its fusion^ 
and possessed of a highly caustic taste. In the matter 
usually called pure potassa by chemists, it exists, com* 
bined with water; and in that commonly called pearl- 



LBCTUBB III. 267 

ashes, or pot-ashes in commerce, it is combined "with a 
small quantity of carbonic acid. Potassa in its uncom- 
bined state, as has been mentioned, page 217, consists 
of the highly inflammable metal potassium and oxygen, 
one proportion of each. 

Soda, or the mineral alkali, is found in some plants 
that grow near the sea; and is obtained combined with 
water, or carbonic acid in the same manner as potassa ; 
and consists of one proportion of sodium, and two 
proportions of oxygen. In its properties it is very 
similar to potassa; but it maybe easily distinguished 
from it by this character : it forms a hard soap with oil : 
potassa forms a soft soap. 

Pearl ashes, and barilla and kelp, or the impure soda 
obtained from the ashes of marine plants, are very 
valuable in commerce, principally on account of their 
uses in the manufacture of glass and soap. Glass is 
made from fixed alkali, flint, and certain metallic sub- 
stances. 

To know whether a vegetable yields alkali, it should 
be burnt, and the ashes washed with a small quantity 
of water. If the water, after being for some time ex- 
posed to the air, reddens paper tinged with turmeric, 
or renders vegetable blues green, it contains alkali. 

To ascertain the relative quantities of pot^ashes af- 
forded by difierent plants, equal weights of them should 
be burnt: the ashes washed in twice their volume of 
water: the washings should be passed through blotting 
paper, and evaporated to dryness. The relative weights 
of the salt obtained will indicate very nearly the 
relative quantities of alkali they contain. 

The value of marine plants in producing soda may 
be estimated in the same manner, with sufficient cor- 
rectness for all commercial purposes. 

n2 



268 AGRICULTUBAL CHEMISTRY. 

Herbs, in general, fumiBh four or five times, and 
shrubs two or three times, as much pot-ashes as trees. 
The leaves produce more than the branches, and the 
branches more than the trunk. V^etables burnt in a 
green state produce more ashes than in a dry state. 

The following table * contains a statement of the 
quantity of pot-ashes afforded by some common trees 
and plants : — 

10,000 parts of Oak - - 15 

Elm - - 39 

Beech - - 12 

Vine - -55 

Poplar . . 7 

Thistle - - 53 

Fern - - 62 

Cow Thistle - 196 

Wormwood - 730 

Vetches - 275 

Beans - - 200 

Fumitory - 760 

TTie earths found in plants are four; silica or the 
earth of flints, alumina or pure clay, lime, and mag- 
nesia. They are procured by incineration. The lime 
is usually combined with carbonic acid. This sub- 
stance and silica are much more common in the vege- 
table kingdom than magnesia, and magnesia more 
common than alumina. The earths form a principal 
part of the matter insoluble in water, afforded by the 
ashes of plants. The silica is known by not being dis- 
solved by acids ; the calcareous earth, unless the ashes 
have been very intensely ignited, dissolves with effer- 
vescence in muriatic acid. Magnesia forms a soluble 

* It is founded apon the experiments of Kirwan, Vanqaelin, and 
Pertuis. 



LECTURE III. 269 

and crystallizable salt, and lime a difficultly soluble one 
with sulphuric acid. Alumina is distinguished from 
the other earths by being acted upon very slowly by 
acids ; and in forming salts very soluble in water^ and 
difficult of crystallization with them. 

The earths appear to be compounds of the peculiar 
metals mentioned in page 218, and oxygen, one propor- 
tion of each. 

The earths a£Porded by plants are applied to no uses 
of common life ; and there are few cases in which the 
knowledge of their nature can be of importance, or 
affi^rd interest to the farmer. 

The only metallic oxides found in plants, are those of 
iron and manganesum : they are detected in the ashes 
of plants ; but in very minute quantities only. When 
the ashes of plants are reddish brown, they abound in 
oxides of iron ; when black or purple, in oxide of man- 
ganesum ; when these colours are mixed, they contain 
both substances. 

The saline compounds contained in plants, or af- 
forded by their incineration, are very various. The 
sulphuric acid combined with potassa, or sulphate of 
potassa, is one of the most usuaL Common salt is 
likewise very often found in the ashes of plants ; like- 
wise phosphate of lime, which is insoluble in water, but 
soluble in muriatic acid. Compounds of the nitric, 
muriatic, sulphuric, and phosphoric acids, with alkalies 
and earths, exist in the sap of many plants, or are 
afforded by their evaporation and incineration. The 
salts of potassa are distinguished from those of soda by 
their producing a precipitate in solutions of platina : 
those of lime are characterized by the cloudiness they 
occasion in solutions containing oxalic acid; those of 
magnesia, by being rendered cloudy by solutions of 



270 



AGRICULTURAL CHEMISTRY. 



ammonia. Sulphuric acid is detected in salts by the 
dense white precipitate it forms in solutions of baryta. 
Muriatic acid by the cloudiness it communicates to 
solution of nitrate of silver; and when salts contain 
nitric acid, they produce scintillations by being thrown 
upon burning coals. 

As no applications have been made of any of the 
neutral salts or analagous compounds found in plants, 
in a separate state, it will be useless to describe them 
individually. The following tables are given from M. 
Th. de Saussure's Researches on Vegetation, and con- 
tain results obtained by that philosopher. They exhibit 
the quantities of soluble salts, metallic oxides, and earths 
afforded by the ashes of different plants : — 



NUDfift of PiUltl. 



Leares of oak (Querou* 

Robur), May 10. 
Ditto, Sept. 27. - 
Wood of young oak. May 

10. - - - - 
Bark of ditto 
Entire wood of oak 
Albamum of ditto 
Bark of ditto 
Cortical layers of ditto - 
Extract of wood of ditto 
Soil fh)in wood of ditto 
Extract from ditto 
Leaves of the poplar(Po- 
puluM niffra)f May 80. * 
Ditto, Sept. 12. - - 
Wood of ditto, Sept. 12. 
Bark of ditto 
Leaves of haiel (Ooryhu 

Avellana), May 1. - 
Ditto washed in cold 

water - - - 
Leaves of ditto, June 22. 
Ditto, Sept. 20. . . 
Wood of ditto, Mayl.- 
Bark of ditto 



i! 



06 652 

93 |fi65 
8 
72 



^1 



^^ 



Constituents of 100 parts of Ashes. 



47 


24 


0.12 


17 


1825 


28 


26 


88-5 


12-25 


7 


4-6 


63-25 


98*0 


4-5 


82 


88 


24 


11 


7 


8 


06 


7 


3-75 


65 


51 






24 


10-5 


10 


06 






36 


IS 


2d 


26 


7 


SG 


— . 


16-76 


87 





5-3 


60 


26 


23-8 


82 


8-2 


10-5 


441 


22-7 


14 


28 


11 


12 


30 


24-5 


35 


8 


12-6 


5-5 


64 





i 




•o 






i 


5 


i 


2 




■g 




"" 


3 


004 


14-5 


1-75 


0-18 


1 


0-25 


1-75 


2 


2-86 


7-6 


2 


1-6 


8 


0-6 


1 


82 


14 


6 


1-85 


11-5 


1-5 


8-8 


1-6 


4 


1-5 


2-5 


1-5 


4 


8 


11-3 


1-5 


22 


2 


0-25 


012 


0-26 


1.75 



25-24 
85-5 

98-56 

28-75 

90^ 

83-5 

81-5 

28.75 

8-5 



i5^r6 

18 

34-6 

8S-2 

84-7 

88-8 

21-5 

17 

32-2 

86 



I 



LECTURE III. 



271 



K&mH of Pluti. 






CanitituanU uf JOi> |wrU t^r A*l0fr 



Bntlpe wood of mullwrry 
(Morui ni(frff\ Not. - 
Altiu mum of ditto 
Barii <jf ditto 
CortkiU U> lira of ditto - 
EnUrp wtjod «f h"m- 

Albamani of ditto 
Bark of dltta 
Wood of horw ch«iDut 
( .£mch1us HijrjfociU' 

Leave* of dUro, Mny 10. 
Leare* of dftto, July ^. 
Ultto^ Scpl, 37. - 
Pioweraof ditto, Maf 10. 
Fruit of dmo. t*ct. B. - 
3A| Piantft of peM (PiJitin 

fcif f i>u.t» )» In flowur - 
PLAjiti of petti {FUvm 

iativutii)^ la flower, 

rJpe ' - 
Flantft of totfrhci ( Vi<tia 

Ftiha\ bcfor* oow&r- 

Jii[r, May S3. 
Ditto, in Bowof, June S3. 

Ditto, ripe, July aa. - 

10 Dillo, Kt>d« Kpantcd - 

tik-i-d* cf ditto 

Ditto, Id flower* rui»ed 
In 4i]titliKl i^iitt'f 

S&lidff&o tt/i^nriij be- 
fore doirerlnK, Mfty 1. 

Djilo, Juftt In flower, 
July IS. - - - 

llitto, Kod^ripe, BcpL 
SO. - * - - 

Plaplfl of tujTiiol (//i{- 

month bcforo flowtT- 
Lng, June 5J3. - 
Dittn* in flowur, July S3, 
Ditto, bearing ripfi vced% 
go|it. W. - 

ruiji,) to tlofcrr 
SO Ditto, wcdi ripij * 
3] DittOt a mguth before 

flowerinRT - - • 
SS DlttOt id flower, June 14. 
33 Ditto, Eeoda r\iH3 ^ 
fU Straw of wbput - 
06 Bwdi of ditifl 



a? 



17 



16 



890 



31 

36 

7 

10 


3-36 
37-36 

8-5 
16-5 


33 

18 
4-5 


38 
86 
4-5 


9-a 

50 
34 

lao 

50 
83 


18 


40-8 


17-35 


34-35 


33 


65-6 

55-5 

60 

43 

01^38 


14-5 
18-5 
17.75 
5-75 
37-93 


601 


80 


67Ji 


10-75 


58 


50 


48 


11 


68 
61 


67 
6 


5-15 


93.6 


4S.25 
11 


13-75 
16 


60 

41 

10 

33-5 

4716 


11-5 
10-75 
11-75 
6-3 
445 



8-5 
4-13 

4 
86 



1-5 
1-6 



11-56 
13-6 



0-35 
0.35 

0-35 
0-35 
0-35 

1 



0-13 
1 

15-35 
0-13 



0-13 
1 
1-5 



1-6 
1-5 
1-75 
1-75 



1-5 
1-5 
8-5 



1.5 
1-5 

8-75 

88 
54 

18-6 
36 
51 
61-6 
0-6 



0-35 
0-35 
113 

1 



3-35 

1 

0.13 



0-35 
1 

3-6 

0-5 
0-5 
0-5 

1 
0,6 

0-5 

0-75 

0-75 

1*5 



0-13 
O'W 

0-5 

0-5 

1 

0«85 

0-6 

0-75 

1 

0*86 



30-88 
21-5 
83-18 
38.38 



36-68 

28 

80-88 



5-85 
34-65 

17:35 

34-50 
3488 
36 
13-9 
3.3 

9-4 

18-85 

31 

18-75 



18-67 
18-78 

17-75 

13-35 
18-75 

15-6 
81-5 
38 
78 
7UJ 



272 



AGRICULTCBAt CHBMISTBY. 









Nftmea of Plants. 


I 


t 

^ 


h 

% be 

il 
la 


i 


s 


1 


1 


1 


1 






1^ 




«-. 












56 
57 






^o 














Bran - • • . 




58 




4-lfl 


46-5 




0-5 


o-«s 


9^ 


Plants of mHlBa (Zea 










May8\ a mon th before 






















flowering, June S9. - 


_ 


188 


— 


09 


5-75 


0-85 


7-5 


0.85 17-25 


68 
50 


Ditto, in flower, July 88. 
Ditto, seeds ripe - - 


— 


61 
46 


— 


09 


6 


0-85 


7'6 


0.85 17 

1 


00 


Stalks of ditto - 


— 


84 


— 


78^ 


5 


1 


18 


0.0 \ 8L05 


61 


Spikes of ditto - 





16 












1 


62 


Seeds of ditto 


— 


10 


— 


08 


80 


_ 


1 


018 <«8 


03 


Chaff of bariej {Hor- 




















deum rmlffare) - 


— 


48 


— 


80 


7-75 


18-5 


07 


0-5 8-S5 


04 


Seeds of ditto - - 





18 


— 


29 


88-5 




85.5 


Qr2& 8-8 


6.; 
00 
87 


Ditto - - - - 
Oats - • - - 


— 


81 


— 


1 


92 

24 


— 


81 
00 


0-18. 90-66 


Leaves of Rhcdodetidron 








0*85 '^-*™ 


1V-/0 




ferrugineum, raised 






















on Jura, a lime-stone 






















mountain, June 20. > 





80 


— 


88 


14 


4825 


0-75 


S^ 


15-08 


68 


Leaves of ditto, raised 
on Breven, a granitic 






















mountain, June 87. - 


«_ 


25 


— 


81-1 


1075 


10^5 


8 


6*77 


81-08 


09 


Branchos of ditto, June 






















80. - - - - 


— 


8 — 1 


82 5 


10 


89 


0-6 


5^ 


8848 


70 


Spikes of ditto, June 87. 


._ 


8 — 1 


84 


11-5 


89 


1 


11 


9«-0 


71 


Leaves of flr (Pint** 
Abici\ misedon Jura, 






















June 80. - - . 


— 


89 


— 


10 


1817 


48-5 


8*0 


1-0 


84-13 


72 


Ditto, raised on Breven, 






















June 87. - - 


_ 


89 


— 


15 


18 


89 


19 


5*5 


19-5 


78 


Branches of Pln& June 
SO. - «■ - 




15 




15 












74 


Whortleberry (raccini- 


"" 
















urn Myrtillut), raised 






















on Jura, Aug. 29. 


— 


26 — 


17 


18 


48 


0-5 


818 


19-88 


75 


Ditto, raised on Breven 


— 


22 1 — 


24 


82 


88 


5 


95 


17-6 



Besides the principles, the nature of which has been 
just discussed, others have been described by chemists 
as belonging to the vegetable kingdom: thus a sub- 
stance, somewhat analogous to the muscular fibre of 
animals, has been detected by Vauquelin in the papaw; 
and a matter similar to animal gelatine, by Braconnot, 
in the mushroom ; ulmin and emetine, sarcocol, nico- 
tine, oUvile, asparagine, inulin, and other bodies, are 



LECTURE III. 273 

generally described in systematic writers on chemistry 
as specific compounds ; but it is likely that few of these 
bodies will retain their places as definite combinations : 
their existence^ likewise^ is extremely limited, and in 
this place it would be improper to dwell upon pecu- 
liarities ; my object being to ofier such general views of 
the constitution of vegetables as may be of use to the 
agriculturist It is probable, fi^m the taste of sarcocol, 
that it is gum combined with a little sugar. Inulin is 
so analogous to starch, that it may be a variety of that 
principle. If slight differences in chemical and phy- 
sical properties be considered as sufficient to establish a 
difference in the species of vegetable substances, the 
catalogue of them might be enlarged to almost any ex- 
tent No two compounds procured firom different vege- 
tables are precisely alike; and there are even differ- 
ences in the qualities of the same compound, according 
to the time in which it has been collected, and the 
manner in which it has been prepared. The great 
use of classification in science is to assist the memory, 
and it ought to be founded upon the similarity of 
properties which are distinct, characteristic, and in- 
variable. 

The analysis of any substance, containing mixtures of 
the different vegetable principles, may be made, in such 
a manner as is necessary for the views of the agricul- 
turist, with fiicility. A given quantity, say 200 grains, 
of the substance, should be powdered, made into a paste 
or mass, with a small quantity of water, and kneaded in 
the hands, or rubbed in a mortar for some time under 
cold water: if it contain much gluten, that principle 
will separate in a coherent mass. After this process, 
whether it has afforded gluten or not, it should be kept 
in contact with half a pint of cold water for three or four 

k5 



274 AGRICULTURAL CHEMISTRY. 

hours, being occasionally nibbed or agitated; the solid 
matter should be separated from the fluid by means of 
blotting-paper. The fluid should be gradually heated; 
if any flakes appear, they are to be separated by the 
same means as the solid matter in the last process, i, e. 
by filtration. The fluid is then to be evaporated to dry- 
ness. The matter obtained is to be examined by ap- 
plying moist paper, tinged with red cabbage juice, or 
violet juice, to it ; if the paper become red, it contains 
acid matter; if it become green, alkaline matter; and 
the nature of the acid or alkaline matter may be known 
by applying the tests described page 262. 267. 268. If 
the solid matter be sweet to the taste, it must be sup- 
posed to contain sugar; if bitterish, bitter principle, or 
extract; if astringent, tannin: and if it be nearly in^- 
pid, it must be principally gum or mucili^. To sepor 
rate gum or mucilage from the other principles, alcohol 
must be boiled upon the solid matter, which will dis- 
solve the sugar and the extract, and leave the mucilage; 
the weight of which may be ascertained. 

To separate sugar and extract, the alcohol must be 
evaporated till crystals b^n to fall down, which are 
sugar ; but they will generally be coloured by some ex- 
tract, and can only be purified by repeated solutions in 
alcohol. Extract may be separated firom sugar, by dis- 
solving the solid, obtained by evaporation from alcohol, 
in a small quantity of water, and boiling it for a long 
while in contact with the air. The extract will grar 
dually fall down in the form of an insoluble powder, and 
the sugar will remain in solution. 

If tannin exist in the first solution made by cold 
water, its separation is easily effected by the process 
described page 248. The solution of isinglass must be 
gradually added, to prevent the existence of an excess 



LBCTURB TIL 275 

of animal jelly in the solation, which might be mistaken 
for mucilage. 

When the vegetable substance^ the subject of experi- 
ment, will afford no more principles to cold water^ it 
must be exposed to hot water. This will unite to 
starchy if there be any, and may likewise take up more 
sugar, extract, and tannin, provided they be intimately 
combined with the other principles of the compound. 

The mode of separating starch is similar to that of 
separating mucilage. 

I^ after the action of hot water, any thing remain, 
the action of boiling alcohol is then to be tried. This 
will dissolve resinous matter; the quantity of which 
may be known by evaporating the alcohol. 

The last agent that may be applied is ether, which 
dissolves elastic gum, though the application is scarcely 
ever necessary; for if this principle be present, it may 
be easily detected by its peculiar qualities. 

If any fixed oil, or wax, exist in the vegetable sub- 
stance, it will separate during the process of boiling in 
water, and may be collected. Any substance not acted 
upon by water, alcohol, or ether, must be regarded as 
woody fibre. 

If volatile oils exist in any vegetable substances, it is 
evident they may be procured, and their quantity ascer- 
tained, by distillation. 

When the quantity of fixed saline, alkaline, metallic, 
or earthy matter in any vegetable compound, is to be 
ascertained, the compound must be decomposed by 
heat, by exposing it, if a fixed substance, in a crucible, 
to a long-continued red heat; and if a volatile sub- 
stance, by passing it through an ignited porcelain tube. 
The nature of the matter so produced may be learnt by 
applying the tests mentioned in Lecture IV* 



276 AGRICULTURAL CHEMISTRY. 

The only analyses in which the agricultural chemist 
can often wish to occupy himself are those of substanced 
containing principally starchy sugar, gluten, oils, muci- 
lage, albumen, and tannin. 

The two following statements will afford an idea of 
the manner in which the results of experiments may be 
arranged. 

The first is a statement of the composition of ripe 
peas, deduced from experiments made by Einhof ; the 
second is of the products afforded by oak bark, deduced 
from experiments conducted by myself: — 

Parts. 

3840 parts of ripe peas afford of starch - 1265 

Fibrous matter analagous to starch, 1 g.^ 

with the coats of the peas - / 

A substance analagous to gluten - 559 

Mucilage - - . 249 

Saccharine matter - - - 81 

Albumen - - - 66 

Volatile matter - - - 540 

Earthy phosphates - - - 11 

Loss - - - - 229 

1000 parts of dry oak bark, from a small tree de- 
prived of epidermis, contain. 

Of woody fibre - - - - 876 

— Tannin - - - - - 57 

— Extract - - - . - 31 

— Mucilage - - - - - 18 

— Matter rendered insoluble during eva- ^ 
poration, probably a mixture of albu- > 9 
men and extract - . J 

— Loss, partly saline matter - - - 29 

To ascertain the primary elements of the different 



LECTURE in. 277 

vegetable principles, and the proportiona in which they 
are combined, different methods of analysis have been 
adopted. The most simple are their decomposition by 
heat, or their formation into new products, by combustion. 

When any vegetable principle is acted on by a strong 
red heat, its elements become newly arranged. Such of 
them as are volatile, are expelled in the gaseous form ; 
and are either condensed as fluids, or remain perma- 
nently elastic. The fixed remainder is either carbo- 
naceous, earthy, saline, alkaline, or metallic matter. 

To make correct experiments on the decomposition 
of vegetable substances by heat, requires a complicated 
apparatus, much time and labour, and all the resources 
of the philosophical chemist; but such results as are 
useful to the agriculturist may be easily obtained. The 
apparatus necessary, is a green glass retort, attached by 
cement to a receiver, connected with a tube passing 
under an inverted jar of known capacity, filled with 
water. * A given weight of the substance is to be heated 
to redness, in the retort over a charcoal fire ; the receiver 
is to be kept cool, and the process continued as long as 
any elastic matter is generated. The condensible fluids 
will collect in the receiver, and the fixed residuum will 
be found in the retort. The fluid products of the dis- 
tillation of vegetable substances are principally water, 
with some acetous and mucous acids, and empyreumatic 
oil or tar, and in some cases ammonia. The gases are 
carbonic acid gas, carbonic oxide, and carburetted hy- 
drogen; sometimes with olefiant gas, and hydrogen; 
and sometimes, but more rarely, with azote. Carbonic 
acid is the only one of those gases rapidly absorbed by 
water; the rest are inflammable ; olefiant gas bums with 
a bright white light ; carburetted hydrogen with a light 
• See Fig. 14. 



278 AGRICULTURAL CHBITISTRT. 

like wax ; carbonic oxide with a feeble blae flame. The 
piopeitieB of hydrogen and aeote, have been described 
in the last Lecture. The specific gravity of carbonic 
acid ga8» is to that of air as 20*7, to 13*7 ; and it con- 
sists of one proportion of carbon 1 1 '4, and two of oxygen 
30. The specific gravity of gaseous oxide of carbon, is, 
taking the same standard, 13'2, and it consists of one 
proportion of carbon, and one of oxygen. The specific 
gravities of carburetted hydrogen and defiant gas, are 
respectively 8 and 13 ; both contain four proportions of 
hydrc^n ; the first contains one proportion, the second 
two proportions of carbon. 

If the weight of the carbonaceous residuum be added 
to the weight of the fluids condensed in the receiver, 
and they be subtracted firom the whole weight of the 
substance, the remainder will be the weight of the 
gaseous matter. 

The acetous and mucous acids and the ammonia 
formed, are usually in very small quantities ; and, by 
comparing the proportions of water and charcoal with 
the quantity of the gases, taking into account their qua- 
lities, a general idea may be formed of the composition 
of the substance. The proportions of the elements in 
the greater number of the vegetable substances which 
can be used as food, have been already ascertained by 
philosophical chemists, and have been stated in the pre- 
ceding pages; the analysis, by distillation, may, how- 
ever, in some cases, be useful in estimating the powers 
of manures, in a manner that will be explained in a 
future Lecture. 

The statements of the composition of vegetable sub- 
stances, quoted firom MM. Gay Lussac and Thenard, 
were obtained by these philosophers, by exposing the 
substances to the action of heated chlorate of potassa ; a 



LfiCTORB in. 279 

body that consists of potassium, chlorine, and oxygen ; 
and which afforded oxygen to the carbon and the hy- 
drogen. Their experiments were made in a peculiar 
apparatus, and required great caution, and were of a 
very delicate nature. It will not, therefore, be necessary 
to enter upon any details of them. 

It is evident, from the whole tenor of the statements 
which have been made, that the most essential vegetable 
substances consist of hydrogen, carbon, and oxygen in 
different proportions, generally alone, but in some few 
cases combined with azote. The acids, alkalies, earths, 
metallic oxides, and saline compounds, though necessary 
in the vegetable economy, must be considered as of less 
importance, particularly in their relation to agriculture, 
than the other principles ; and, as it appears from M. 
de Saussure's table, and fix>m other experiments, they 
differ in the same species of vegetable when it is raised 
on different soils. 

MM. Gay Lussac and Thenard have deduced three 
propositions, which they have called laws, from their 
experiments on vegetable substances. TTie first is, 
^^ That a vegetable substance is always acid whenever 
the oxygen it contains is to the hydrogen in a grater 
proportion than in water." 

The second, ** That a vegetable substance is always 
resinous, or oily or spirituous, whenever it contains 
oxygen in a smaller proportion to the hydrogen, than 
exists in water." 

The Mrdy ^* That a vegetable substance is neither acid 
nor resinous, but is either saccharine or mucilaginous, 
or analogous to woody fibre or starch, whenever the 
oxygen and hydrogen in it are in the same proportions 
as in water." 

New experiments upon other vegetable substances. 



280 AGRICULTURAL CHEMISTRY. 

besides those examined by MM. Gay Lassac and Tbe'> 
nard, are required before these interesting conclusions 
can be fully admitted. Their researches establish, how- 
ever, the close analogy between several vegetable 
compounds differing in their sensible qualities, and 
combined with those of other chemists, offer simple 
explanations of several processes in nature and art, by 
which different vegetable substances are converted into 
each other, or changed into new compounds. 

Gum and sugar, excluding the different proportions 
of water they may contain, afford nearly the same ele- 
ments by analysis ; and starch differs from them only in 
containing a little more carbon. The peculiar proper- 
ties of gum and sugar, must depend chiefly upon the 
different arrangement or degree of condensation of their 
dements ; and it would be natural to conceive, from the 
composition of these bodies, as well as that of starch, 
that all three would be easily convertible one into the 
other; which is actually the case. 

At the time of the ripening of com, the saccharine 
matter in the grain, and that carried from the sap ves- 
sels into the grain, become coagulated, probably simply 
by losing water, and form starch. And, in the process 
of malting, the converse change occurs. The starch of 
grain is converted into sugar. As there is a little ab- 
sorption of oxygen, and a formation of carbonic acid in 
this case, it is likely that the starch loses a little carbon, 
which combines with the oxygen to form carbonic acid ; 
and probably, the oxygen tends to acidify the gluten of 
the grain, and thus breaks down the texture of the 
starch ; gives a new arrangement to its elements, and 
renders it soluble in water. 

Mr. Cruikshank, by exposing syrup to a substance 
named phosphuret of lime, which has a great tendency 



LBCTURE III. 284 

to decompose water^ converted a part of the sugar into 
a matter analogous to mucilage. And M. Kirchhoff, re- 
cently, has converted starch into sugar by a very simple 
process, that of boiling in very diluted sulphuric acid. 
The proportions are 100 parts of starch, 400 parts of 
water, and 1 part of sulphuric acid by weight. This 
mixture is to be kept boiling for 40 hours ; the loss of 
water by evaporation, being supplied by new quantities. 
The acid is to be neutralized by lime ; and the sugar 
crystallized by cooling. This experiment has been tried 
with success by many persons. Sir C. Tuthill, from a 
pound and a half of potatoe starch, procured a pound 
and a quarter of crystalline, brown sugar; which he 
conceives possessed properties intermediate between 
cane-sugar and grape-sugar. 

It is probable from the experiments of M. Theodore 
de Saussure, that the conversion of starch into sugar, 
in this experiment, is effected merely by its combination 
with water ; for his experiments prove that the acid is 
not decomposed, and that no elastic matter is set fi«e, 
and that the sugar weighs more than the starch from 
which it is formed : probably the colour of the sugar, is 
owing to the disengagement, or new combination of a 
little carbon, the slight excess of which, as has been 
just stated, constitutes the only difference (independent 
of the different quantities of water they may contain) 
perceptible by analysis between sugar and starch. 

M. Bouillon la Grange, by slightly roastii^ starch, 
has rendered it soluble in cold water; and the solution 
evaporated afforded a substance, having the characters 
of mucilage. And by experiments similar to those 
of M. Kirchhoff, M. Braconnot has lately shown that 
saccharine and mucilaginous substances may be pro- 
cured from various forms of woody fibre; and I 



282 AGRICULTURAL CHEMISTRY. 

have seen specimens of soft sugar made from linen 
rags- 
Gluten and albumen differ from the other vegetable 
products, principally by containing asote. When gluten 
is kept long in water, it undergoes fermentation; am- 
monia (which contains its azote) is given off with 
acetic acid ; and a fatty matter and a substance ana- 
logous to woody fibre remain. 

Extract, tannin, and gallic acid, when their solutions 
are long exposed to air, deposit a matter similar to 
woody fibre; and the solid substances are rendered 
analogous to woody fibre, by slight roasting ; and in 
these cases it is probable that part of their oxygen and 
hydrogen is separated as water. 

All the other vegetable principles differ from the 
vegetable acids in containing more hydrogen and 
carbon, or less oxygen: many of them, therefore, 
are easily converted into vegetable acids by a mere 
subtraction of some proportions of hydrogen. The 
vegetable acids, for the most part, are convertible into 
each other by easy processes. The oxalic contains 
most oxygen; the acetic the least; and this last sub- 
stance is easily formed by the distillation of other 
vegetable substances, or by the action of the atmo- 
sphere on such of them as are soluble in water ; pro- 
bably by the mere combination of oxygen with hy- 
drogen and carbon, or in some cases by the subtraction 
of a portion of hydrogen. 

Alcohol, or spirits of wine, has been often mentioned 
in the course of these Lectures. This substance was not 
descriebd amongst the vegetable principles, because it has 
never been found ready formed in the organs of plants. 
It is procured by a change in the principles of sacchar 
rine matter, in a process called vinous fermentation. 



LECTURE III. 283 

The expressed juice of the grape contams sugar, 
mucilage, gluten, and some saline matter, principally 
composed of tartaric acid : when this juice, or musty as 
it is commonly called, is exposed to the temperature of 
about 70^, the fermentation begins; it becomes thick 
and turbid; its temperature increases, and carbonic 
acid gas is disengaged in abundance. In a few days the 
fermentation ceases ; the solid matter that rendered the 
juice turbid falls to the bottom, and it clears ; the sweet 
taste of the fluid is in great measure destroyed, and it 
becomes spirituous. 

Fabroni has shown that the gluten in must is essential 
to fermentation ; and that chemist has made saccharine 
matter ferment, by adding to its solution in water, 
common vegetable gluten and tartaric acid. Gay 
Lussac has demonstrated that must will not ferment 
when freed from air by boiling, and placed out of the 
contact of oxygen ; but that fermentation begins as 
soon as it is exposed to the oxygen of air, a little of 
that principle being absorbed; and that it then con- 
tinues independent of the presence of the atmosphere. 
In the manufacture of ale and porter, the sugar 
formed during the germination of barley is made to 
ferment by dissolving it in water with a little yeast, 
which contains gluten in the state proper for producing 
fermentation, and exposing it to the requisite tempera- 
ture; carbonic acid gas is given off as in the fer- 
mentation of must, and the liquor gradually becomes 
spirituous. 

Similar phenomena occur in the fermentation of the 
sugar in the juice of apples and other ripe fruits. It 
appears that fermentation depends entirely upon a new 
arrangement of the elements of sugar; part of the 
carbon uniting to oxygen to form carbonic acid, and the 



284 AGRICULTURAL CHEMISTRY. 

remaining carbon, hydrogen, and oxygen, combining 
as alcohol ; and the use of the gluten or yeast, and the 
primary exposure to air, seems to be to occasion the 
formation of a certain quantity of carbonic acid ; and 
this change being once produced is continued; its 
agency may be compared to that of a spark in pro- 
ducing the inflammation of gunpowder; the increase of 
temperature occasioned by the formation of one 
quantity of carbonic acid occasions the combination of 
the elements of another quantity. 

From the experiments of M. Theodore de Saussure 
it appears that alcohol is composed of 100 parts of 
defiant (or percarburetted hydrogen gas,) and of 
63*58 water, or oxygen and hydrogen in the propor- 
tions necessary to form water. 

Alcohol, in its purest known form, is a highly in- 
flammable liquid, of specific gravity 796, at the tem- 
perature of 60**; it boils at about 170° Fahrenheit. 
This alcohol is obtained by repeated distillation of the 
strongest common spirit from the salt called by che- 
mists muriate of lime, it having been previously heated 
red-hot 

The strongest alcohol obtained by the distillation 
of spirit without salts has seldom a less specific gravi^ 
than 825 at 60° ; and it contains, according to Lowitz*s 
experiments, 89 parts of the alcohol of 796, and 11 
parts of water. The spirit established as froof spirii 
by act of parliament passed in 1762 ought to have the 
specific gravity of 916; and this contains nearly equal 
weights of pure alcohol and water. 

The alcohol in fermented liquors is in combination 
with water, colouring matter, sugar, mucilage, and the 
vegetable acids. It has been often doubted whether it 
can be procured by any other process than distillation ; 



LECTURE III. 286 

and some persons have even supposed that it is formed 
by distillation. The experiments of Mr. Brande are 
conclusive against both these opinions. That gentle- 
man has shown that the colouring and acid matter in 
wines may be, for the most part, separated in a solid 
form by the action of a solution of sugar of lead (ace- 
tate of lead), and that the alcohol may then be obtained 
by abstracting the water by means of hydrate of potassa 
or muriate of lime, without artificial heat. 

The intoxicating powers of fermented liquors depend 
on the alcohol that they contain ; but their action on 
the stomach is modified by the acid, saccharine, or 
mucilaginous substances they hold in solution* Alcohol 
probably acts with most efficacy when it is most loosely 
combined; and its enei^ seems to be impaired by 
union with large quantities of water, or with sugar or 
acid, or extractive matter. 

The table in the following page contains the results 
of Mr. Brande's experiments on the quantity of alcohol 
of 825 at 60°, in different fermented liquors. 

The spirits distilled from different fermented liquors 
differ in their flavour : for peculiar odorous matter, or 
volatile oils, rise in most cases with the alcohoL The 
spirit from malt usually has an empyreumatic taste like 
that of the oil, formed by the distiUation of vegetable 
substances. The best brandies seem to owe their flavoiur 
to a peculiar oily matter, formed probably by the action 
of the tartaric acid on alcohol; and rum derives its 
characteristic taste from a principle in the sugar cane. 



286 



AORICULTCBAL CHEMISTRY. 





Proportion 




Proportioo 


Wine. 


of Alcohol 


Wine. 


of Alcohol 


per cent, by 


per cent by 




measure. 




measure. 


Port 


1900 


Frontignac - 


12-79 


Ditto 


21-40 


Coti Roti . 


12-32 


Ditto 


22-30 


Roussillon - 


17-26 


Ditto 


23-39 


Ditto 


19-00 


Ditto 


23-71 


Cape Madeira 


18-11 


Ditto 


24-29 


Ditto 


20-50 


Ditto 


26-83 


Ditto 


22-»4 


Average 


22-96 


Cape Muscat 


18-26 


Madeira 


19-24 


White Constantia - 


19-76 


Ditto (Sercial) 


21-40 


Red Constantia 


18-92 


Ditto 


23-93 


Tent 


13-30 


Ditto 


24-42 


Sheraaz 


16-52 


Average 


22-27 


Syracuse - 


16-28 


Sherry 


18-25 


Nice 


14-63 


Ditto 


18-79 


Tokay 


9-88 


Ditto 


19-81 


Lissa 


26-47 


Ditto 


19-83 


Ditto 


24-35 


Average 


1917 


Teneriffe - 


19-79 


Claret 


12-91 


Colares 


19-75 


Ditto 


14-08 


Lachryma Christi - 


19-70 


Ditto 


16-32 


Vidonia 


19-25 


Ditto 


17-11 


Alba flora - 


17-26 


Average 


16-10 


Zante 


17-06 


Calcarella • 


1810 


Lunel 


15-52 


Ditto 


19-20 


Sauteme 


14-22 


Lisbon 


18-94 


Barsac 


13-86 


Malaga 


17-26 


Raisin Wine 


25-77 


Ditto 


18-94 


Ditto 


26-40 


Bucellaa 


18-49 


Ditto 


12a-20 


Red Madeira 


18-40 


Orange Wine 


11-28 


Ditto 


22-30 


Grape Wine 


1811 


Malnifley Madeira - 


16-40 


Currant Wine 


20-55 


Marsala - 


2505 


Gooseberry Wine - 


11-84 


Ditto 


26-03 


Elder Wnie - 


8-79 


Red Champagne - 


11-30 


Mead 


7-32 


Ditto 


12-56 


Cyder 


9-87 


White Champagne - 


12-80 


Ditto 


5-21 


Still Champagne - 


13-80 


Perry 


7-26 


Burgundy - 


14-53 


Brown Stout 


6-80 


Ditto 


11-95 


Ale (Burton) 


8-88 


Ditto 


15-22 


Edinburgh 


6-20 


Ditto 


16-80 


Dorchester 


5-56 


White Hermitage - 


17-43 


London Porter 


4-20 


Red Hermitage 


12-32 


Small Beer 


1-28 


Hock 


14-37 


Brandy 


63-39 


Ditto 


1300 


Rum 


53-68 


Ditto 


8-88 


Hollands . 


51-60 


Vin de Grave 


12-80 


Scotch Whisky 


64-32 


Ditto 


13-94 


Irish Whisky 


63-90 



LECTURE III. 287 

All the common spirits may, I find, be deprived of 
their peculiar flavour by repeatedly digesting them with 
a mixture of well-burnt charcoal and quicklime ; they 
then afford pure alcohol by distillation. The cognac 
brandies, I find, contain vegetable prussic acid, and 
their flavoiu: may be imitated by adding to a solution of 
alcohol in water of the same strength, a few drops of 
the ethereal oil of wine produced during the formation 
of ether,''^ and a similar quantity of vegetable prussic 
acid procured firom laurel leaves or any bitter kernels. 

I have mentioned ether in the course of this Lecture ; 
this substance is procured from alcohol by distilling a 
mixture of equal parts of alcohol and sulphuric acid. 
It is the lightest known liquid substance, being of spe- 
cific gravity 632 at 60^. It is very volatile and rises in 
vapour, even by the heat of the body. It is highly 
inflammable. In the formation of ether it is most pro- 
bable, from the experiments of M. de Saussure, that 
the elements of water merely are separated from the 
alcohol by the sulphuric acid, and that ether differs 
from alcohol in containing a larger proportion of carbon 
and hydrogen. Like alcohol, it possesses intoxicating 
powers. 

A number of the changes taking place in the vege- 
table principles depend upon the separation of oxygen 
and hydrogen as water from the compound ; but there 
is one of very great importance, in which a new combi- 
nation of the elements of water is the principal opera- 
tion. This is in the manufacture of bread. When any 
kind of flour, which consists principally of starch, is 

* In the process of the distillation of alcohol and sulphuric acid after 
the ether is procured ; by a higher degree of heat, a yellow fluid is pro- 
duced ; which Is the substance in question. It has a fragrant smell and 
an agreeable taste. 



288 AGRICULTUBAL CHEMISTRY. 

made into a paste with water, and immediately and 
gradually heated to aboot 440^, it increases in weight, 
and is found entirely altered in its properties ; it has 
lost its solubility in water, and its power of being 
converted into sugar. In this state it is unleavened 
bread. 

When the flour of com or the stareh of potatoes, 
mixed with boiled potatoes, is made into a paste with 
water, kept warm, and suffered to remain 30 or 40 
hours, it ferments, carbonic acid gas is disengi^^ed finom 
it, and it becomes fiUed with globules of elastic fluid. 
In this state it is raised dough, and affords, by baking, 
leavened bread ; but this bread is sour and disagreeable 
to the taste; and leavened bread for use is made by 
mixing a little dough, that has fermented, with new 
dough, and kneading them together, or by kneading the 
bread with a small quantity of yeast 

In the formation of wheaten bread more than \ of 
the elements of water combine with the flour; more 
water is consolidated in the formation of bread firom 
barley, and still more in that from oats ; but the gluten 
in wheat, being in much larger quantity than in other 
grain, seems to form a combination with the stareh and 
water, which renders wheaten bread more digestible 
than the other species of bread. 

The arrangement of many of the vegetable principles 
in the different parts of plants has been incidentally 
mentioned in this Lecture ; but a more particular state- 
ment is required to afford just views of the relation 
between their organization and chemical constitution, 
which is an object of great importance. The tubes and 
hexagonal cells in the vascular system of plants are 
composed of woody fibre ; and when they are not filled 
with fluid matter they contain some of the solid mate- 



LECTURE III. 289 

rials which formed a constitaent part of the fluids be- 
longing to them. 

In the roots, trunk, and branches, the bark, albur- 
num, and heart-wood, the leaves and flowers, the great 
basis of the solid parts is woody fibre. It forms by &x 
the greatest part of the heart-wood and bark ; there is 
less in the- alburnum, and still less in the leaves and 
flowers. The alburnum of the birch contains so much 
sugar and mucilage, that it is sometimes used in the 
north of Europe as a substitute for bread. The leaves 
of the cabbage, broccoli, and sea-cale contain much 
mucilage, a little saccharine matter, and a little albumen. 
From 1000 parts of the leaves of common cabbage I 
obtained 41 parts of mucilage, 24 of sugar, and 8 of 
albuminous matter. 

In bulbous roots, and sometimes in common roots, 
a large quantity of starch, albumen, and mucilage are 
ofi;en found deposited in the vessels ; and they are most 
abundant after the sap has ceased to flow ; and afford a 
nourishment for the early shoots made in spring. The 
potatoe is the bulb that contains the largest quanti^ of 
soluble matter in its cells and vessels ; and it is of most 
importance in its application as food. Potatoes in 
general afford from ^ to ^^ their weight of dry starch. 
From 100 parts of the common Kidney potatoe^ Dr. 
Pearson obtained from 32 to 28 parts of meal, which 
contained from 23 to 20 of starch and mucilage : and 
100 parts of the Apple potatoe^ in various experiments, 
afibrded me from' 18 to 20 parts of pure starch. From 
5 pounds of the variety of the potatoe called Captain 
harty Mr. Skrimshire, jun. obtained 12 oz. of starch ; 
from the same quantity of the Bauffh red potatoe, 10|^ 
oz. ; from the Moultan wMtCy 11|-; from the Yorkshire 
kidney y 10^ oz. ; from Hundred eyes, 9 oz, ; from Purple 

VOL. vu. o 



890 AGRICULTURAL CHEHISTBT. 

red, S^; from Ox noble, S\. The other soluble mb- 
stances in the potatoe are albumen and vmcilagew 

From the analysis of Einhoff it appears that 7680 
parts of potatoe afford, 

OfStarch .... 1163 

-** Fibrous matter analogous to stardi - 540 
— Albumen - - . - 107 

-^ Mucilage in the state of a saturated so* *! 
lution - • - -J 

2122 

So that a 'fourth part of die ^veight of the potatoe at 
least may be considered as nutritive matter* Sfir. 
Knight informs me, that he has found the best i>otatoeB^ 
such as the Irish apple, to possess mudi greater specific 
gravity, varying from 1075 to 1100 ; and it is {»t>bable 
that their nutritive properties are nearly proportioiiate 
to their specific gravitiesu 

The turnip, carrot, and panmep, afford principally 
saccharine, mucilaginous, and extractive matt». I ob«* 
tained firom 1000 parts of common turnips, 7 parta of 
mneilage, 84 of saodiarine matter, and neariy 1 part i)£ 
albumen ; 1000 parts of carrots iumished 95 parts of 
sugar, 3 parts of mucilage, cmd i part of extract ; 1000 
parts of parsnep afforded 80 parts of saccharine maH<^ 
and 9 parts of mucilage ; the JFakherm or v>kiie emftdt 
gave, in 1000 parts, 98 parts of sugar, 2 parts f£ vmfi* 
lage, and 1 of extract 

Fruits, in the organization of their soft parts, $}>- 
proach to the natmne of bulbs. They contain a certain 
quantity of nourishment laid up in their cells for the 
use of the embiyon plant ; mucilage, sugar, starcl^ ai^ 
found in many of them often cofnluned inth v^taUe 
acids. Most of the fruit trees common in Britain hl^v^ 



LBCTCrai IXL 291 

been naturalized on account of the saccharine matter 
they contain, which, united to the vegetable acids and 
mucilage, renders them at once agieeable to the taste, 
astd nutritiTe. 

The Taliie of fruits for the manufaotuw of fermented 
liquors may be judged of from the ipeoific gravity of 
their expressed juices ; but the quantity of jmoe and 
the consistence of the pulp differ ivideiy in different 
species of fruits, and therefore the specific grayity of 
the fruit will not always indicate 'the "falue of its fer- 
mented produce. The best cyder and perry are made 
from those apples and pears that aSord the densest 
juices ; and a compariaon between different fruits may 
be made with tolerable accuracy by plunging them to- 
gether into a saturated solution of salt, or a strong solu- 
tion of sugar; those Aat sink deepest will afford the 
richest juice. 

Starch, or coagulated mucilf^e, forms the greatest 
part of the seeds and grains used for food ; and Aey are 
generally combined with gluten, oU, or albuimnous 
matter. In com, with gluten ; in peas and beans, with 
albuminous matter ; and in rape^seed, hemp seed. Un- 
seed, and the kernels of most nuts, with oils. 

I found 100 parts of good full^grained wheat sown in 
autunm to afford 

Of Starch - 77 

— Gluten 19 

lOD parts of wheat sown in spring. 

Of Starch - 70 

^ Gluten - 24 

100 parts of Barbary wheat. 

Of Starch - 74 

-^ Gluten - 23 

o2 



292 AGRICUI/rURAL CHEMISTRY. 

100 parts of Sicilian wheat, / 

Of Starch - 75 

— Gluten - 21 

I have examined dififerent specimens of North Ame- 
rican vrheat ; all of them have contdned rather more 
gluten than the British. In general, the wheat of wana 
climates abounds more in gluten, and in insoluble parts; 
and it is of greater specific gravity, harder, and more 
difficult to grind. 

The wheat of the south of Europe, in ccmsequence 
of the larger quantity of gluten it contains, is peculiarly 
fitted for making macaroni, and other preparations of 
flour, in which a glutinous quality is considered as an 
excellence. 

In some experiments made on barley, I obtained firom 
100 parts of full and fair Norfolk barley. 

Of Starch - - - 79 

— Gluten - . - 6 

— Husk - . , 8 

The remaining 7 parts saccharine matter. The 
sugar in barley is probably the chief cause why it 
is more proper for malting than any other species of 
grain. 

Einhoff has published a minute analysis of barley 
meal. He found in 3840 parts. 

Of volatile matter - - 360 

— Albumen - - - 44 

— Saccharine matter - - 200 

— Mucilage - - - 176 

— Phosphate of lime, with some albumen 9 

— Gluten - ' - 135 

— Husk, with some gluten and starch - 260 

— Starch not quite fi^e firom gluten - 2580 

— Loss - - - 78 



LECTURE m. 293 

Rye afforded to Emhoff^in 3840 parts, 2520 meal, 

930 husk, and 390 moisture ; and the same quantity of 
meal analysed gave. 

Of Starch . - . 2346 

— Albumen - - - 116 

— Mucilage - • - 426 

— Saccharine - - * 126 

— Gluten not dried - - 364 
Remainder husk and loss. 

I obtained from 1000 parts of rye, grown in Suffolk, 
61 parts of starch and 5 parts of gluten. 

100 parts of oats, from Sussex, afforded me 59 parts 
of starch, 6 of gluten, and 2 of saccharine matter. 

1000 parts of peas, grown in Norfolk, afforded me 
501 parts of starch, 22 parts of saccharine matter, 35 
parts of albuminous matter, and 16 parts of extract, 
which became insoluble during evaporation of the saccha- 
rine fluid. 

From 3840 parts of marsh beans ( Viciafaba), Einhoff 
obtained. 

Of Starch - - - 1312 

— Albumen - - - 31 

— other matters which may be con- 
ceived nutritive ; such as gummy. 



con-^ 
imy,f 

LS tO| 



1204 

starchy, fibrous matter analogous '^^ 

animal matter 

The same quantity of kidney beans (Fhaseoltis vul- 
garii), afforded. 

Of matter analogous to starch - 1805 

— Albumen and matter approaching 1 
to animal matter in its nature - J 

— Mucilage - - - - 799 
From 3840 parts of lentiles, he obtained 1260 parts 



2M AORICUUTITRII CBfiMISTRY. 

of Starchy and 143S of « mattter analogous to animal 
matter. 

The matter analagous to animal matter la desi^ibed by 
EinhojQP, as a glutinous substance insoluUe in water ; 
soluble in alcohol; when dry, having the apf>eanuice of 
glue ; probably a peculiar modification of gluten. 

From 16 parts of hempseed, Buchok obtained 3 parts 
of oil^ 3^ parts of albumen^ about l-f of saccharine and 
gummy matter. The insoluble hulks and coats of the 
seeds weighed 6^ parts. 

The different parts of flowers contain different 8ul> 
stances : the pollen^ or impregnating dust of the date, 
has been found by Fourcroy and Vauquelin to contain 
a matter analagous to gluten, and a soluble extract 
abounding in malic acid* Link found in the pollen of 
the hazel-tree, much tannin and gluten. 

Saccharine matter is found in the nectarium of flowers, 
or the receptacles within the corolla, and by tempting 
the larger insects into the flowers, it renders the work 
of impregnation more secure ; for the pollen is often by 
their means applied to the stigma ; and this is particu- 
larly the case when the male and female organs are in 
different flowers or different plants. 

It has been stated, that the firagrance of flowers de- 
pends upon the volatile oils they contain ; and these 
oils, by their constant evaporation, surround the flower 
with a kind of odorous atmosphere ; which, at the same 
time that it entices larger insects, may probably preserve 
the parts of fructification from the ravages of smaller ones. 
Volatile oils, or odorous substances, seem particularly 
destructive to these minute insects and animalcules which 
feed on the substance of vegetables: thousands of 
aphides may be usually seen in the stalk and leaves of 
the rose ; but none of them are ever observed on the 



LECTUBB IIL 295 

flower. Camphor is used to preserve the coUectioism of 
naturalists. The woods that contain aromatic oils ate 
remarked for their indestructibility, and for their ex- 
emption from the attacks of insects: this is particularly 
the case with the cedar, rose-wood, and cypress. The 
gates of Constantinople, which were made of this last 
wood, stood entire from the time of Constantine^ their 
founder, to that of Pope Eugene IV., a period of 1100 
years. 

The petab of many flowers aflbid saccharine and 
mucilaginous matter. The white lily yields mucilage 
abundantly ; and the orange lily a ouzture of mucilage 
and sugar ; the petab of the convolvulus afford sugar, 
mucilage^ and albuminous matter. 

The chemical nature of the colouring matters of 
flowers has not as yet been subject to any veiy accurate 
observation. These colouring matters, in general, are 
very transient, particularly the blues and reds ; alkalies 
change the colours of most flowers to green, and acids 
to led. An imitation of the colouring matter may be 
made by digesting solutions of gall-nuts with chalk : a 
green fluid is obtained, which becomes red by the acticm 
of an acid ; and has its green colour restored by means 
of alkalies. 

The yellow colouring matters of flowers are the most 
permanent ; the carthamus contains a red and a yellow 
colouring matter : the yellow colouring matter is easily 
dissolved by water ; and from the red, rouge is prepared 
by a process which is kept secret 

The same substances as exist in the solid parts of 
plants are found in their fluids, with the exception of 
woody fibre. Fixed and volatile oils, containing resin 
or camphor, or analogous substances in solution, exist 
in the cylindrical tubes belonging to a number of plants. 



296 AGBICULTURAL CHBMISTRT. 

Different species of Euphorbia emit a milky juice, which 
when exposed to air deposits a substance analogous to 
starchy and another, similar to gluten. 

Opium, glim elastic, gamboge, the poisons of the 
Upas Antiar and Tieute, and other substances that exude 
from plants, may be considered as pecidicd* juices be- 
longing to appropriate vessels. 

The sap of plants, in general, is very compound in 
its nature ; and contains more saccharine, mucilaginous;, 
and albuminous 'matter in the alburnum; and most 
tannin and extract in the bark. The cambium, which 
is the mucilaginous fluid found in trees between the 
wood and the bark, and which is essential to the formsr 
tion of new parts, seems to be derived from these two 
kinds of sap; and probably is a combination of the mu- 
cilaginous and albuminous matter of one, with the 
astringent matter of the other, in a state fitted to be- 
come organized by the separation of its watery parts. 

The albumous saps of some trees have been chemi- 
cally examined by Vauquelin. He found in those of 
the elm, beech, yoke elm, hornbeam, and birch, extrac- 
tive and mucilaginous matter, and acetic acid combined 
with potassa or lime. The solid matter afforded by 
their evaporation yielded an ammoniacal smell, pro- 
bably owing to albumen : the sap of the birch afforded 
saccharine matter. 

Deyeux in the sap of the vine and the yoke elm has 
detected a matter analogous to the curd of milk. I 
found a substance similar to albumen in the sap of the 
walnut tree. 

I found the juice which exudes from the vessels of 
the marsh-mallow when cut, to be a solution of muci- 
l^e. 

The fluids contained in the sap vessels of wheat and 



LECTUBE III. 297 

bairley^ afforded in some experiments which I made on 
them, mucilage, sugar, and a matter which coagulated 
by heat; which last was most abundant in wheat 

The following table contains a statement of the quan- 
tity of soluble or nutritive matters existing in varieties 
of the different substances that have been mentioned, 
and of some others which are used as articles of food, 
either for man or cattle. The analyses are my own ; 
and were conducted with a view to a knowledge of the 
general nature and quantity of the products, and not of 
their intimate chemical composition. The soluble mat- 
ters afforded by the grasses, except that from the fiorin 
in winter, were obtained by Mr. Sinclair, gardener to 
the Duke of Bedford, from given weights of the grasses 
cut when the seeds were ripe : they were sent to me by 
his Grace's desire for chemical examination, and form 
part of the results of an important and extensive series 
of experiments on grasses made by the. direction of the 
Duke, at Wobum Abbey, when pursuing those plans for 
the improvement of agriculture, the origin of which 
has thrown so much glory on the memoiy of his illus- 
trious brother. 

All these substances were submitted to experiment 
green, and in their natural states. It is probable that 
the excellence of the different articles, as food, will be 
found to be in a great measure proportional to the 
quantities of soluble or nutritive matters they afford ; 
but still these quantities cannot be regarded as absolutely 
denoting their value. Albuminous or glutinous matters 
have the characters of animal substances ; sugar is more 
nourishing, and extractive matter less noiuishing, than 
any other principles composed of carbon, hydrogen, and 
oxygen. Certain combinations likewise of these sub- 
stances may be more nutritive than others. 

o5 



298 



AGRICUUrUBAL CHEMISTRY. 



Table of Ae QumtiHes cf Soluble or Nutritive Matten 
bg 100 Farti of different Vegetable Subetamcee. 













Extnei 




Whole 








orJIatta 


VegetebleB or Vegetable 
Siibiteiioe. 


C^oaatityof 

Soluble or 
Katritite 


MacOage oi 
Starch. 


?J~~f Gluten 01 


leuknd 

inaofaibk 

dmiBg 




Matter. 








atko. 


Middleflex wheat, ftTer- 












age crop 


055 


765 





190 




Spring wheat - 


MO 


700 


— 


240 




Mildewed wheat of 1806 


210 


178 





32 




Blighted wheat of laoi 


660 


690 





190 




TUelL-tklaoed Siciliaa 












wheat of 1810 


055 


726 





230 




TMn-^kliiMd Sicffian 












wheat of 1810 


061 


722 


-» 


239 




Wheat from Poland - 


050 


750 





200 




Narth Amtrlcaa wheat 


MS 


790 


-> 


996 




Norfolk barley 


020 


790 


70 


60 




Oats ftpom Scotfatnd - 


743 


641 


16 


87 




Rye from YarkAin - 


703 


646 


36 


109 




Conunon bean 


670 


426 


— 


103 


41 


DrypeM 


574 


601 


92 


95 


16 


Potetoee 


5 ftom 260 
tto200 


(from 900 
(to 165 


(from 20 
^tol5 


i fromiO 
(to 30 






161 


199 


11 


17 




Red beet 


148 


14 


121 


13 




White beet - 


196 


19 


119 


4 




Parsnep 


98 





00 






Carrots 


00 


3 


96 








42 


7 


94 


1 




Bwedieh tunups 


64 


9 


61 


2 


i 


Cabbage 


73 


41 


24 


8 




Bvoad^laared clover - 


99 


91 


9 


9 




Long-rooted clover 


39 


30 


4 


3 




White cloyer - 


32 


20 


1 


3 




Sainfoin 


90 


2B 


2 


8 




Lucerne 


23 


18 


1 


.^ 




Meadow fox-tail grass 


98 


24 


8 





6 


Perennial rye grass - 


80 


26 


4 


— 






78 


66 


6 









99 


^ 


6 


-^ 


J 


Crested dog'B-4aU grass 


35 


28 


3 


— 


4 


Spiked fbscue grass - 


19 


15 


2 


— 






82 


72 


4 


— 


6 1 


Sweet-scented Temal 












grass 


50 


49 


4 


— 


I 1 


Florin 


64 


46 


6 


1 


i 1 


Fiorin cat in winter - 


76 


64 


8 


1 ' 


_l^ 



LBOTUBB III. 280 

I have been ii^onned by Sir Joseph Banks, that the 
Derbyshire miners, in winter, prefer oat-cakes to wheaten 
bread; finding that this kind of nourishment enables 
them to support their strength and perform their Libour 
better. In summer, they say oat-cake heats them, and 
they then consume the finest wheaten bread they can 
procure. Even the skin of the kernel of oats probably 
has a nourishing power, and is rendered partly soluble 
in the stomach with the starch and gluten. In most 
countries of Europe, except Britain, and in Arabia, 
bosses are fed with com of different kinds» mixed with 
dioi^>ed straw; and the chopped straw seems to act the 
same part as the husk of the oat In the mill 14 lbs. of 
good wheat yield on an average 13 lbs. of flour ; the 
same qnanti^ of barley 12 lbs., and of oats only 8 lbs. 

In the South of Europe, hard or thin-skinned wheat is 
in higher estimation, than soft or thick-skinned wheat; 
the reason of which is obvious, fi'om the larger quantity 
of gluten and nutritive matter it contains. I have made 
an analysis of only one specimen of thin-skinned wheat, 
so that other specimens may possibly contain more nu- 
tritive matter Uian that m the table ; the Barbary and 
Sicilian wheats, brfore referred to, were thick-skinned 
wheats. In England, the di£Sculty of grinding thin- 
skinned wheat is an objection; but this difficulty is 
easily overcome by moistening the com.* 

* For the following note on this snhject I am indebted to the kindness 
of the Right Hon. Sir Joseph Banks, Bart., E.B.: — 

Iitformatkm received from John Jeffrey ^ -Sf^., Aif Mqjeit^e ConnU- 
General at Lisbon^ in Annoer to Queries transmitted to him, from 
the Comm, ofP.C.for Trade, dated Jan. 12, 1812. 

'' To grind hard com with the miU-stones used in England, the wheat 
mnjit be well screened, then sprinkled with water at the miller's dis- 
cretion, and laid in heaps and frequently turned and thoroughly mixed. 



300 AORICULTUBAL CHSHISTRT. 

which will lofteii the hiuk| so as to make it separate from the floor in 
grindingy and of course give the flour a brighter colour ; otherwuse the 
flinty quality of the wheat, and the thinness of the skin will prevent its 
separation, and wiU render the flour unfit for making into bread. 

'< I am informed by a miller of considemble experience, and who works 
his mills entirely with the stones from England or Ireland, that he fre- 
quently prepares the hard Barbary com by immersing it in water in 
close wicker baskets, and spreading it thinly on a floor to dry ; much 
depends on the judgment and skill of the miller in preparing llie com for 
the mill according to its relatlTe quality. I beg to observe, that it ia not 
from this previous process of wetting the com that the weight in the 
flour of hard com is increased ; but from its natural quality it imbibes 
considerably more water in making it into bread. The mill-stones must 
not be cut too deep, but the fttrrows very flne, and picked in the osual 
way. The mills should work with less velocity in grinding hard com 
than with soft, and set to work at first with soft com, till the mill ceases 
to work well ; then put on the hard com. Hard wheat always sells at a 
higher price in the market than soft wheat, on an average of ten to fifteen 
per cent ; as it produces more flour in proportion, and less bran than 
the soft com. 

" Flour made from hard wheat is more esteemed than what is made 
from soft com ; and both sorts are applied to every purpose. 

** The flour of hard wheat is in general superior to that made from 
soft; and there ir'no difference in the process of making them into 
bread ; but the flour from hard wheat will imbibe and retain more water 
in making into bread, and will consequently produce more weight of 
bread : it is the practice here, and which I am persuaded it would be 
advisable to adopt in England, to make bread with flour of hard and 
soft wheat, which by being mixed, will make the bread much better. 

(Signed) « JOHN JEFFREY." 



301 



LBCTURE IV. 

On Soila : their Constitaeiit Parts.— On the Analysis of soils.— Of the 
Uses of the SoO.— Of the Rocks and Strata found beneath the Soils.— 
Of the Improyement of Soil. 

No subjects are of more importance to the fiurmer than 
the nature and improvement of soils ; and no parts of 
the doctrines of agriculture are more capable of being 
lUuslarated by chemical inquiries. 

Soils are extremely diversified in appearance and 
quality; yet, as it was stated in the Litroductoiy Lec- 
ture^ they consist of different proportions of the same 
elements ; which are in various states of chemical com- 
bination, or mechanical mixture. 

The substances which constitute soils have been 
already mentioned. They are certain compounds of 
the earths, silica, lime, alumina, magnesia, and of the 
oxides of iron and manganesum ; animal and vegetable 
matters in a. decomposing state, and saline, acid, or 
alkaline combinations. 

In all chemical experiments on the composition of 
soils connected with agriculture, the constituent parts 
obtained are compounds : and they act as compounds 
in nature : it is in this state, therefore, that I shall de- 
scribe their characteristic properties. 

1. SiUca, or the earth oiJUnts^ in its pure and crys- 
tallized form, is the substance known by the name of 
rock crystal, or Cornish diamond. As it is procured by 



302 AGRICULTUIUL CHBMISTRT. 

chemists, it appears in the form of a white impalpable 
powder. It is not soluble in the common acid^ bat 
dissolves by heat in fixed alkaline lixivia. It is an in- 
combustible substance, for it is saturated with oxygen. 
I have proved it to be a compound of oxygen and the 
peculiar combustible body which I have named silicum; 
and from the experiments of Berzelius, it is probable 
that it contains nearly equal weights of these two 
elements. 

2. The sensible properties of lime are well known« 
It exists in soils usually united to carbonic acid, which 
is easily disengaged from it l^ the attraction of the 
common acids. It is sometimes found combined with 
the phosphoric and sulphuric acids. Its chemical pio- 
perties and agencies in its pure state will be dfacrihed 
in the lecture on manures obtained Srom the mineral 
kingdom. It is soluble in nitric and muriatic adds, and 
fi)rms a substance with sulphuric acid difficult of soht- 
tion, called gypsum. It is not soluble in alkaline solu- 
tions. It consists of one {Hioportion 40 of the pecu- 
liar metallic substance^ which I have named rj^Xmi^tn ; 
and ooe proportion 15 of oxygen. 

3. Ahamna exists in a puce and crystallized state in 
the white sapphire, and united to s little oxide of iron 
and silica in the other oriental gems. In the state in 
which it is procured by chemists, it aj^axs as a white 
powder, soluble in acids and .fixed alkaUne liquors. 
From my experiments, it appears that alumina consists 
of one proportion 33 of aluminnm, and one 15 of 
oxygen. 

4. Magnesia exists in a pure crystallized state, con- 
stituting a mineral like talc found in Nortji America. 
In its common form it is the magnesia tit^o, or calcined 
magnesia of druggists. It generally exists in soils 



UCTUBJB IV. MS 

oomluiied with carixmic acicL It i« soluble in all th* 
mineral acids ; but not in alkaline lixivia. It is distinr 
gnished from the other earths found in soils by its ready 
•olubility in solutions of alkaline carbonates^ saturattd 
with carbonic add. It appears to consist of 38 ma^ 
nesium and 15 oxygen. 

5. There are two well-known oaadss ofircn, the Uack 
and the brown. The black is the substance that flies 
off when red-hot iron is hammered. The brown pxide 
may be formed by keeping the Uack oxide red^^hot fi>r 
a long time in contact with air. The first seems to 
consist of one proportion of iron lOS, and two of 
oxygen dO; and the second of one proportion of iron 
103^ and three proportions of oxygen 45. The oxides 
of iron aometimes exist in bchIs combined with carbonic 
acid. They are easily distingtiishftd from other soIh 
•tanoes by their giving, when dissolved in acids, a Uack 
colour to solution of galls, and a bright blue piecipitate 
to solution of prussiate of poitassa and iron. 

6. The oxide of manffoaetum is the substance com- 
monly called manganese, and used in bleaching. It 
appears to be composed of one proportion of mangane*- 
8um 113, and three of oxygen 45. It is distingnished 
from the other substances found in soils, by its proper^ 
of decomposing muriatic add, and converting it into 
chlcMTine. 

7. VegettxbU ani animal matters are known by their 
sensible qualities, and by their property of being de- 
composed by heat, llieir characters may be learnt 
from the details in the last lectuse. 

9. The saline eompcnmds found in soils, are common 
salt, sulphate of magnesia, sometimes sulphate of ijK«, 
nitrates of Eme and of magnesia, sulphate of potassa, 
and carbonates of potassa and soda. To describe their 



304 AOBICULTURAL CHBMISTBT. 

cliancten minutely will be unnecessary: the tests for 
most of them haye been noticed, p. 269. 

The silica in soils is osoally combined with alumina 
and oxide of iron, or with alumina, lime, magnesia^ and 
oxide of iron, forming gravel and sand of different 
degrees of fineness. The carbonate of lime is usually 
in an impalpable form ; but sometimes in the state of 
calcareous sand. The magnesia, if not combined in 
the gravel and sand of soil, is in a fine powder united 
to carbonic acid. The impalpable part of the soil, 
which is usually called clay or loam, consists of silica, 
alumina, lime, and magnesia; and is, in fiu^t, usually of 
the same composition as the hard sand, but more finely 
divided. The vegetable or animal matters (and the 
first is by £ur the most common in soils,) exist in dif- 
ferent states of decomposition. They are sometimes 
fibrous, sometimes entirely broken down and mixed 
with the soiL 

To form a just idea of soUs, it is necessary to cGa- 
ceive different rocks decomposed, or ground into parts 
and powder of different degrees of fineness, some of 
their soluble parts dissolved by water, and that water 
adhering to the mass, and the whole mixed with larger 
or smaller quantities of the remains of v^etables and 
animals in different stages of decay. 

It will be necessary to describe the processes by 
which all the varieties of soils may be analysed. I 
shall be minute in these particulars, and, I fear, tedious : 
but the philosophical fiirmer will, I trust, feel the pro* 
priety of full details on this subject. 

The instruments required for the analysis of soils are 
few, and but little expensive. They are, a balance 
capable of containing a quarter of a pound of common 
soil, and capable of turning when loaded with a grain ; a 



LBCnTRB lY. 305 

set of weights firom a quarter of a pound troy to a grain ; 
a wire sieve^ sufficiendy coarse to admit a mustard seed 
through its apertures; an Argand lamp and stand; 
some glass bottles; Hessian crucibles; porcelain, or 
queen's ware evaporating basins ; a Wedgewood pestle 
and mortar; some filters made of half a sheet of blot- 
ting paper^ folded so as to contain a pint of liquid, and 
greased at the edges ; a bone knife, and an apparatus 
for collecting and measuring aeriform ffuids. 
. The chemical substances or reagents required for 
separating the constituent parts of the soil, have, for 
the most part, been mentioned before ; they are murir 
atic acid {spirit of salt), sulphuric acid, pure volatile 
alkaU dissolved in water, solution of prussiate of potash 
and iron, succinate of ammonia, soap lye, or solution of 
potassa, solutions of carbonate of ammonia, of muriate 
of ammonia, of neutxvl carbonate of potadi, and nitrate 
of ammonia. 

In cases when the general nature of the soil of a 
field is to be ascertained, specimens of it should be 
taken firom different places, two or three inches below 
the sur&ce, and examined as to the similarity of their 
properties. It sometimes happens, that upqn plains the 
whole of the upper stratum of the land is of the same 
kind, and in this case one analysis will be sufficient ; 
but in valleys, and near the beds of rivers, there are 
very great differences, and it now and then occurs that 
one part of a field is calcareous, and another part 
siliceous ; and in this case, anch in analc^ous cases, the 
portions different firom each other should be sepa- 
rately submitted to experiment 

Soils, when collected, if they cannot be immediately 
examined, should be preserved in phials quite filled 
with them, and closed with ground-glass stoppers. 



806 AGRICULTtTltAL CHEMISTRY. 

The quantity of soil most oonvenient for a perfect 
analysis, is from two to four bundled grains. It should 
be collected in dry weather^ and exposed to the atmo- 
sphere till it becomes dry to the touch. 

The specific gravity of a soil, or the relation of its 
weight to that of water, may be ascertained by intro^ 
duoing into a phial, which will contain a known qoan* 
tity of water, equal volumes of water and of soil ; and 
this may be easily done by pouring in water till it is 
half full, and then adding the soil till the fluid rises to 
the mouth ; the difference between the weight of the 
soil and that of the water will give the result Thu^ 
if the bottle oontains four hundred grains of water, 
and gains two hundred grains when half filled with 
water and half with soil, the specific gravity of the boU 
will be 2 ; that is, it will be twice as heavy as water; 
and if it gained 165 grains, its specific gravity would be 
1825, water being 1000. 

It Is of importance that the specific gravity of a soil 
should be known, as it afibrds an indication of the 
quantity of animal and vegetable matter it contains; 
these substances being always most abundant in the 
lighter soils. 

The other physical properties of soils should likewise 
be examined before the analysis is made, as they denote, 
to a certain extent, their composition, and serve as guides 
in directing the experiments. Thus, siliceous soils 
are generally rough to the touch, and scratch glass whai 
rubbed upon it; ferruginous soils are of a red or yellow 
colour; and calcareous soils are soft. 

1. Soils, though as dry as they can be made by con- 
tinued exposure to air, in all cases still contain a con- 
siderable quantity of water, which adheres with great 
obstinacy to the earths and animal and vegetable matter. 



LBCnnts nr. 807 

and can only be driven off from them by a considerable 
degrae of heat. The first process of analysis is, to firee 
the given weight of soil from as much of this water as 
possible without in other respects affecting its composi- 
tion ; and this may be done by heating it for ten or 
twelve minutes over an Avgand's lamp, in a basin of 
porcelain, to a temperature equal to 300 Fahrenheit; 
and if a thermometer is not used, the proper degree may 
be easily ascertained, by keeping a piece of wood in 
contact with the bottom of the diish; as long as the 
colour of the wood remains unaltered, the heat is not 
too high ; but when the wood begins to be charred, the 
process must be stopped. A small quantity of water 
will, perhaps, remain in the soil even after this opera- 
tion, but it always afibrds useftd comparative results ; 
and if a higher temperature were employed, the vege- 
table or animal matter would undergo decomposition, 
and in consequence the experiment be wholly unsatis- 
fcctory. 

The loss of weight in the process should be carefully 
noted5 and when in 400 grains of soil it reaches as 
high as 00, the soil may be considered as in the greatest 
degree absorbent, and retentive of water, and will 
generally be found to contain much vegetable or 
animal matter, or a large proportion of aluminous 
earth. When the loss is only from 20 to 10, the land 
may be considered as only slightly absorbent and 
retentive, and siliceous earth probably forms the 
greatest part of it 

2. None of the loose stones, gravel, or large vege- 
table fibres, should be divided from the pure soil till 
after the water is drawn off; for these bodies are 
themselves of^n highly absorbent and retentive, and^ in 
consequence, influence the fertility of the land. The 



308 AGRICULTUIUL CHEMISTRY. 

next process, however, after that of heating, should he 
their separation, which may be easily accomplished by 
the sieve, after the soil has been gently braised in a 
mortar. The weights of the vegetable fibres or wood, 
and of the gravel and stones, should be separately noted 
down,, and the nature of the last ascertained; if cal- 
careous, they wiU effervesce with acids; if siliceous 
they will be sufficiently hard to scratch glass ; and if of 
the common aluminous class of stones, diey will be 
soft, easily cut with a knife, and incapable of ef- 
fervescing with acids. 

3. The greater number of soils, besides gravel and 
stones, contain larger or smaller proportions of sand of 
different degrees of fineness; and it is a necessary 
operation, the next in the process of analysis, to detach 
them firom the parts in a state of more minute division, 
such as clay, loam, marie, vegetable and animal matter, 
and the matter soluble in water. This may be effected 
in a way sufficiently accurate, by boiling the soil in 
three or four times its weight of water ; and when the 
texture of the soil is broken down, and the water cool, 
by agitating the parts together, and then suffering them 
to rest In this case, the coarse sand will generally 
separate in a minute, and the finer in two or three 
minutes, whilst the highly divided earthy, animal, or 
vegetable matter, will remain in a state of mechanical 
suspension for a much longer time ; so that by pouring 
the water firom the bottom of the vessel, after one, two, 
or three minutes, the sand will be principally separated 
firom the other substances, which, with the water con- 
taining them, must be poured into a filter, and after the 
water has passed through, collected, dried, and weighed. 
The sand must likewise be weighed, and the respective 
quantities noted down. The water of lixiviatibn must 



LECTURE IV. 309 

be preserved, as it will be found to contain the saline 
and soluble animal or vegetable mattersy if any exist 
in the soiL 

4. By the process of washing and filtration, the soil 
is separated into two portions, the most important ot 
which is generally the finely-divided matter. A minute 
analysis of the sand is seldom or never necessary, and 
its nature may be detected in the same manner as that 
of the stones or gravel. It is always either siliceous 
sand, or calcareous sand or a mixture of both. If it 
consist wholly of carbonate of lime, it will be rapidly 
soluble in muriatic acid, with effervescence ; but if it 
consist partly of this substance, and partly of siliceous 
matter, the respective quantities may be ascertained by 
weighing the residuum after the action of the acid, 
which must be applied till the mixture has acquired a 
sour taste, and has ceased to effervesce. This residuum 
is the siliceous part ; it must be washed, dried, and 
heated strongly in a crucible ; the difference between 
the weight of it and the weight of the whole indicates 
the proportion of calcareous sand. 

5. The finely-divided matter of the soil is usually 
very compound in its nature ; it sometimes contains all 
the four primitive earths of soils, as well as animal and 
vegetable matter; and to ascertain the proportions of 
these with tolerable accuracy is the most difficult part of 
the subject. 

The first process to be performed in this part of the 
analysis is the exposure of the fine mattcfr of the soil to 
the action of muriatic acid. This substance should be 
poured upon the earthy matter in an evaporating basin, 
in a quantity equal to twice the weight of the earthy 
matter ; but diluted with double its volume of water. 
The mixture should be often stirred, and suffered to 



810 AGRICULTTTBAL CHXMI8TBT. 

mnain for an hour, or an hoar and a half, bdc»e 
it 18 examined. 

If anj carbonate of lime or of magnesia exist in the 
toil, ihej will have been dissdved in this time by the 
acid, wlideh aometimes takes up likewise a little oxide of 
lion ; but very seldom any alumina. 

The fluid sboukl be passed through a filter; the 
solid mattar colleetad, washed with rain*water, dried «t 
a moderate heat, and weighed. Its loss will denote the 
quantity of solid matter taken up. The washings moat 
be added to the solution, which, if not sour to Ae 
taste, must be made so by the addition of fiesh acid» 
when a little solution oi prusaiate of potaasa and inm 
must be mixed with the whole. K a Uue precipitate 
occurs, it denotes the presence of oxide cf iron, and 
the solution of the prussiate must be dropped in tffl 
no farther effect is produced. To ascertain its quanti^, 
it must be collected in the same manner as other solid 
precipitates, and heated red; the result is oxide nf 
iron, which may he mixed with a litde oxide of man- 
ganesum. 

Into the fluid freed from oxide of iron, a sototion of 
neutralixed carbonate of potassh must be poured, till ail 
eftsrvesoence ceases in it, and till its taste and aniell 
indicate a considerable excess of alkaline salt. 

The precipitate that &lk down is carbonate of Hmft ; 
it must be collected on the fidter, and dried «t a heat 
below that of rednen. 

The remaining fluid must be boiled for a quavter 
of an hour, when the magnesia, if any eadst, wiU 
be precipitated from it, oombined with carbonic aoid, 
and its quantity is to be ascertained in the same 
manner as that of the carbonate of lime. 

If any minute proportion of alumina should, fiKun 



PLATy. ft 



. V/ 



/V>/. A> 




fl'lill 



LECTURS IV. 311 

peculiair-circumstances, be dissolved by the acid^ it will 
be found in the precipitate with the carbonate of lime, 
and it may be separated from it by boiliog it for a few 
minutes with soap-lye, sufficient to cover the solid 
matter: this substance dissolves alumina, without 
acting upon carbonate of lime. 

Should the finely^divided soil be sufficiently cal- 
careous to effervesce very strongly with acids, a very 
aitnple method may be adopted for ascertaining the 
quantity of carbonate of lime, and one sufficiently 
acQurate in all common cases. 

Carbonate of lime, in all its states, contains a deter- 
minate proportion of carbonic acid, t. e. nearly 43 per 
cent, so that when the quantity of this elastic fluid 
givw out by any soil during the solution of its cal- 
careous matter in an acid is known» either in weight or 
measure, the quantity of carbonate of lime m^y be 
easily discovered. 

When the process, by diminution of weight, is em- 
ployed, two parts of the acid, and one part of the mat- 
tor of the soil, must be weighed in two separate bottles, 
^nd very slowly mixed tc^ether till the effervescence 
ceases: the difference between their weight before 
and after the experiment denotes the quantity of car- 
bonic acid lost; for every four grains and a quarter 
of which, ten grains of carbonate of lime must be esti- 
mated. 

The best method of colleoting the carbonic add, so as to 
discover its volume, is by a peculiar pneumatic apparatus,* 

t Ftg. 15. A, B, C, iD, represent the dUIbrent paits of this ttpparattis. 
A represents the bottle fbr recelylng the soil. B the bottle containing 
the acid^ famished with a stop-cock. G the tube eonnteted with a 
flaccid bladder. I) the graduated measnre. E the botUe for con- 
taining the bladder. When this instrument is used, a given quantity of 



312 AGRIGULTUEAL CHEHI8TBT. 

in which its bulk may be measured by the quanti^ of 
water it displaces. 

6. After the calcareous parts of the soil have been 
acted upon by muriatic acid, the next process is to as- 
certain the quantity of finely-divided insoluble animal 
and vegetable matter that it contains. 

This may be done with sufficient precision^ by strongly 
igniting it in a crucible over a common fire till no 
blackness remains in the mass. It should be often stir- 
red with a metallic rod, so as to expose new surfaces 
continually to the air : the loss of weight that it under- 
goes denotes the quantity of the substance that it con- 
tains destructible by fire and air. 

It is not possible, without very refined and difficult 
experiments, to ascertain whether this substance is 
wholly animal or vegetable matter, or a mixture of both. 
When the smell emitted, during the incineration, is 
similar to that of burnt feathers, it is a certain indica- 
tion of some substance either animal, or analagous to 
animal matter; and a copious blue flame, at the time of 
ignition, almost always denotes a considerable propor- 
tion of vegetable matter. In cases when it is necessary 
that the experiment should be very quickly performed, 

•oil iB introdaced into A. B is fUled with muriatic acid dilated wHh 
an eqnal quantity of water ; and the stop-cock being closed, is connected 
with the npper orifice of A, which is gpnound to receive it. The tabe D 
is introdaced into the lower orifice of A, and the bladder connected with 
it placed in its flaccid state into E, which is filled with water. The gra- 
duated measure is placed under the tube of £. When the stop-cock of 
B is turned, the acid flows into A, and acts upon the soil ; the elastic 
fluid gencndly passes through C into the bladder, and displaces a quan- 
tity of water in £ equal to it in bulk, and this water flows through the 
tube into the graduated measure ; and gives by its volume the indicar 
tion of the proportion of carbonic acid disengaged from the soil ; for 
every ounce measure of which two grains of carbonate of lime^may be 
estimated. 



LEcrruBE IV. 313 

the destruction of the decomposable substances may be 
assisted by the agency of nitrate of ammonia, which, 
at the time of ignition, may be thrown gradually upon 
the heated mass, in the quantity of twenty grains for 
every hundred of residual soil. It accelerates the dis* 
sipation of the animal and vegetable matter, which it 
causes to be converted into elastic fluids ; and it is it- 
self, at the same time, decomposed and lost. 

7. The substances remaining after the destruction of 
the vegetable and animal matter, are generally minute 
particles of earthy matter, containing usually alumina 
and silica, with combined oxide of iron, or of manga* 
nesum. 

To separate these from each other, the solid matter 
should be boiled for two or three hours with sulphuric 
acid, diluted with four times its weight of water ; the 
quantity of the acid should be regulated by the quan- 
tity of solid residuum to be acted on, allowing for every 
100 grains 2 drachms, or 120 grains of acid. 

The substance remaining after the action of the acid 
may be considered as siliceous ; and it must be sepa- 
rated, and its weight ascertained, after washing and 
drying in the usual manner. 

The alumina and the oxide of iron and manganesum, 
if any exist, are all dissolved by the sulphuric acid : they 
maybe separated by succinate of ammonia, added to 
excess, which throws down the oxide of iron; and by 
soap lye, which will dissolve the alumina, but not the 
oxide of manganesum ; the weights of the oxides, as- 
certained after they have been heated to redness, will 
denote their quantities. 

Should any magnesia and lime have escaped solution 
in the muriatic acid, they will be found in the sulphu- 
ric acid; this, however, is rarely the case; but the pro- 

VOL. VII. P 



314 AORICULTCRAL CHEMISTRY. 

<ȣs for detecting them, and ascertainiiig their quan- 
tities, is the game in both instances. 

The method of analysis, by salphoric acid, is snf- 
ficientiy precise for all usual experiments; but if veiy 
great accuracy be an object, dry carbonate of potaaaa 
must be employed as the agent, and the residuum of the 
incineration (6) must be heated red for half an hour, 
with four times its weight of this substance, in a cru^ 
cible of silver, or of well-baked porcelain. The mass 
obtained must be dissolved in- muriatic acid, and the so- 
lution evaporated till it is nearly solid; distilled water 
must then be added, by which the oxide of iron^ and all 
the earths, except silica, will be dissolved in combina- 
tion as muriates. The silica, after the usual process of 
Hxiviation, must be heated red ; the other substances 
may be separated in the same numner as from the muri- 
atic apd sulphuric solutions. 

This process is the one usually employed by diemical 
philosophers for the analysis of stones. 

8. If any saline matter, or soluble vegetable or animal 
matter, is suspected in the soil, it will be found in the 
water of lixiviation used for separating the sand. 

This water must be evaporated to dryness in a proper 
dish, at a heat below its boiling point. 

If the solid matter obtained is of a brown colour and 
inflammable, it may be considered as partly vegetaUe 
extract If its smell, when exposed to heat, be like 
liiat of burnt feathers, it contains animal or albuminous 
matter; if it be white, crystalline, and not destructible 
by heat, it may be considered as principally saline 
matter ; the nature of which may be known by the 
tests described, p. 2^9. 

9. Should sulphate or phosphate of lime be suspected 
in the entire soil, the detection of tliem requires a par- 



LECTURB IV. 315 

tkular process upon it A given weight of it, for in- 
atanoe 400 gridns, must be heated red for half an hour 
in a crucible, mixed yviih one-third of powdered char- 
coal. The mixture must b^ boiled for a quarter of an 
hour, in a half pint of w:ater, and the fluid collected 
through the filtre, and exposed for some days to the 
atmosphere in an open vessel. If any notable quantity 
of sulphate of lime (^y/>^7n) existed in the soil, a white 
precipitate will gradually form in the fluid, and the 
weight of it will indicate the proportion. 

Phosphate of lime, if any exist, may be separated 
from the soil after tl^ process for gypsum. Muriatic 
acid must be digested upon the soil, in quantity more 
dian sufficient to saturate the soluble earths; the solu- 
don must- be evaporated, and water poured upon the 
solid matter. This fluid will dissolve the compounds of 
earths with the muriatic acid, and leave the phosphate 
of lime untouched. It would not fall within the limits 
assigned to this lecture to detail any processes lor the 
detection of substances which may be accidentally 
mixed with the matters of soils. Other earths and 
metallic oxides are now and then found in them, but in 
quantities too minute to bear any relation to fertility 
or barrenness, and the search for them would make the 
analysis much more complicated, without rendering it 
more usefol. 

10. When the examination of a soil is completed, 
the products should be numerically arranged, and their 
quantities added together; and if they nearly equal 
the original quantity of soil, the analysis may be con- 
sidered as accurate. It must, however, be noticed, that 
when phosphate or sulphate of lime are discovered by 
the independent process just described (9), a correc- 
tion must be made for the general process, by subtract- 

p 2 



316 AGRICULTUEAL CHBMI8TRT. 

ing a sum equal to their weight from the quantity of 
carbonate of lime obtained by precipitation from the 
muriatic acid. 

In arranging the products, the form should be in the 
order of the experiments by which they were pro- 
cured. 

Thus, I obtained from 400 grains of a good siliceous 
sandy soil from a hop-garden near Tunbridge, Kent, — 







Grains. 


Of water of absorption 


- 


19 


Of loose stones and gravel, principally 






siliceous - . - 


- 


53 


Of undecompounded vegetable fibres 


- 


14 


Of fine siliceous sand 


- 


212 


Of minutely divided matter separated 






by agitation and filtration, and 






consisting of — 






Carbonate of lime - - - 


19 




Carbonate of magnesia 


3 




Matter destructible by heat, princi- 






pally vegetable 


15 




Silica . - -. - 


21 




Alumina .. - - - 


13 




Oxide of iron - - - 


5 




Soluble matter, principally common 






salt and vegetable extract 


3 




Gypsum - - - - 


2 






— 


81 


Amount of all the products 


379 


Loss 


- 


21 



LECTURE IV. 317 

The loss in this analysis is not more than usually 
occurs, and it depends upon the impossibility of col- 
lecting the whole quantities of the diflferent precipi- 
tates, and upon the presence of more moisture than is 
accounted for in the water of absorption, and which is 
lost in the different processes. 

When the experimenter is become acquainted with 
the use of the different instruments, the properties of 
the reagents, and the relations between the external 
and chemical qualities of soils, he will seldom find it 
necessary to perform, in any one case, all the processes 
that have been described. When his soil, for instance, 
contains no notable proportion of calcareous matter, 
the action of the muriatic acid (7) may be omitted* In 
examining peat soils, he will principally have to attend to 
the operation by fire and air (8); in the analysis of 
chalks and loams, he will often be able to omit the ex- 
periment by sulphuric acid (9); and when a soil is 
extremely dense and heavy, and after being heated to 
redness, strongly attracted by the magnet, he must par- 
ticularly attend to the quantity of iron it contains; and, 
in this case, the muriatic acid will be the principal 
agent. 

In the first trials that are made by persons unac- 
quainted with chemistry, they must not expect much 
precision of result Many difficulties will be met with; 
but in overcoming them, the most useful kind of prac- 
tical knowledge will be obtained; and nothing is so 
instructive in experimental science as the detection of 
mistakes. The correct analyst ought to be well grounded 
in general chemical information ; but, perhaps, there is 
no better mode of gaining it, than that of attempting 
original investigations. In pursuing his experiments, 
he will be continually obliged to learn the properties of 



318 AGRICULTURAL CHEMISTRY. 

the substances he is emplbymg or acting upon ; «id his 
theoretical ideas will be more vduable in. being cxm- 
nected with practical opefatibns, and acquired for the 
purpose of discovery. 

Plants, being possessed of no locomotive pewters, can 
grow only in places where they are suppHed with food ; 
and the soil is necessary to their existence, both aa 
affording them nourishment and enabling them to fix 
themselves in such a manner as to obey those mechanic 
cal laws by which their radicles aiie kept below the aor- 
hce, and their leaves exposed to the fiee atmo^>here. 
As the systems of roots, branches, and leaves are very 
different in diffsrent vegetables, so they flourish most 
in different soils; the plants that have bulbous roots 
require a looser and lighter soil than such as have 
fibrous roots; and the plants possessing only short 
fibrous radicles demand a firmer soil than such as have 
tap roots, or extensive lateral roots. 

A good turnip soil from Holkham, Norfolk, afforded 
me 8 parts, out of 9 sUiceous sand; and the finely 
divided matter consisted of 



Carbonate of lime 


• 


- 63 


Silica 


- 


. 15 


Alumina 


. 


- 11 


Oxide of iron - 


- 


- 3 


Vegetable and saline matter 


- 


- 5 


Moisture 


- 


- 3 



I found the soil taken finom a field at Sieffield 
Place in Sussex, remlurkable tor producing flouradiing 
onks, to consist of six parts of sand, and one part cf 
clay and finely divided matter. And 100 parts of the 
entire soil submitted to analysis produced. 



LECTUUB IV. 




319 


Silica - . - 


• 


- 64 


Alumina - . ^ 


• 


. 28 


Carbonate of lime - 


• 


- 3 


Oxide of iron 


m 


- 5 


Decomposing vegetable matter 


- 


- 4 


Moisture and loss 


- 


- 6 



An excellent wheat soil from the neighbourhood of 
West Drayton^ Middlesex, gave 3 parts in 5 of siliceous 
sand ; and the finely divided matter consisted of 

Carbonate of lime - - - - 28 

Silica 32 

Alumina - - - - - 29 

Animal or vegetable matter and moisture - II 

Of these soils the last was by &r the most, and the 
first the least, coherent in texture. In all cases the 
constituent parts of the soil which give tenacity and 
coherence are the finely divided matters; and they 
possess the power of giving those qualities the highest 
d^ree when they oontain much alumina. A small 
quantity of finely divided matter is sufficent to fit a 
soil for the production of turnips and barley ; and I 
have seen a tolerable crop of turnips on a soil contain- 
ing 11 parts out of 12 sand. A much greater propor- 
tion of sand, however, always produces absolute sterility. 
The soil of Bagshot Heath, which is entirely devoid of 
vegetable covering, contains less than -^ of finely 
divided matter. 400 parts of it which had been heated 
red, aJBTorded me 380 parts of coarse siliceous sand, 9 
parts of fine siliceous sand, and 11 parts of impalpable 
matter, which was a mixture of ferruginous clay with 
carbonate c£ lime. Vegetable or animal matters, when 
finely divided, not only give coherence, but likewise 
softness and penetrability; but neither they nor any 



320 AGRICULTURAL CHBHISTRT. 

Other part of the soil must be in too great proportion ; 
and a soil is unproductive if it consist entirely of im- 
palpable matter. 

Pure alumina, or silica, pure carbonate of lime^ or 
carbonate of magnesia, are incapable of supporting 
healthy vegetation. 

No soil is fertile that contains as much as 19 parts 
out of 20 of any of the constituents that have been 
mentioned. 

It will be asked, are the pure earths in the soil merely 
active as mechanical, or indirect chemical agents, or do 
they actually afford food to the plant ? This is an im- 
portant question ; and not difficult of solution. 

The earths consist, as I have before stated, of metals, 
united to oxygen; and these metals have not been 
decomposed ; there is consequently no reason to sup- 
pose that the earths are convertible into the elements 
of organized compounds, into carbon, hydrogen, and 
azote. 

Plants have been made to grow in given quantities 
of earth. They consume very small portions only, and 
what is lost may be accounted for by the quantities 
found in their ashes ; that is to say, it has not been 
converted into any new products. 

The carbonic acid united to lime or magnesia, if any 
stronger acid happens to be formed in the soil during 
the fermentation of vegetable matter, which will disen* 
gage it from the earths, may be decomposed : but the 
earths themselves cannot be supposed convertible into 
other substances by any process taking place in the 
soil. 

In all cases the ashes of plants contain some of the 
earths of the soil in which they grow ; but these earths, 
as may be seen from the table of the ashes afforded by 



LECTtJRE IV. 321 

difiierent plants given in the last lecture, never equal 
more than 3-^ of the weight of the plant consumed. 

If they be considered as necessary to the vegetable, 
it is as giving hardness and firmness to its organization. 
Thus, it has been mentioned that wheat, oats, and 
many of the hollow grasses, have an epidermis princi- 
pally of silicepus earth ; the use of which seems to be 
to strengthen them, and defend them from the attacks 
of insects and parasitical plants. 

Many soils are popularly distinguished as cold; and 
the distinction, though at first view it may appear 
to be founded on prejudice, is really just 

Some soils are much more heated by the rays of the 
sun, all other circumstances being equal, than others ; 
and soils brought to the same degree of heat cool in 
different times, ue. some cool much faster than others. 

This property has been very little attended to in a 
philosophical point of view; yet it is of the highest im- 
portance in agriculture. In general, soils that consist 
principally of a stiff white clay are difficultly heated ; 
andT being usually very moist, they retain their heat 
only for a short time. Chalks are similar in one respect, 
that they are difficultly heated ; but being drier they 
retain their heat longer, less being consumed in causing 
the evaporation of their moisture. 

A black soil, containing much soft vegetable matter, 
is most heated by the sun and air ; and the coloured 
soils, and the soils containing much carbonaceous mat- 
ter, or ferruginous matter, exposed under equal circum- 
stances to the sun, acquire a much higher temperature 
than pale-coloured soils. 

When soils are perfectly dry, those that most readily 
become heated by the solar rays likewise cool most 
rapidly, their power of losing heat by radiation being 

p5 



328 AGBICUXTURAL CHSmSTRT. 

greatest; bat I hare asceTtai]ie<^ by experiment, diat 
the darisest coloured diy soily (that which contaiiv 
aboodanoe of animal C€ yegetaUe matter, sobetanoes 
which most fiKdlitate the dimination of temperatnre,) 
when heated to the same degree, provided it be within 
the common limits of the effect of solar heiU, will cool 
more slowly than a wet pale soil, entirely coihposed of 
earthy matter. 

I found that a rich Uack mould, which, contuned 
neariy i of the T^etaUe matter, had its temperatme 
increased in an hour fiom 65^ to 88^ by exposure to 
sunshine; whilst a chalk S(m1 was heated only to 69^ 
under the same circumstances. But the mould re- 
moved into the shade, where the temperature was 62?, 
lost, in half an hour, 15^; whereas the chalk, under the 
same circumstances, had lost only 4°. 

A brown fertile soil and a ocdd barren day were each 
artificially heated to 88% having been previously dried : 
they were then exposed in a temperature of 57^ ; in 
half an hour the dark soil was fimnd to have lost 9^ of 
heat; the clay had lost only 6% An equal portion of 
the clay containing moisture, after being heated to 88% 
was exposed in a temperature of 55^ ; in less than a 
quarter of an hour, it was found to have gained the 
temperature of the room. The soils in all these ex- 
periments were placed in small dn-j^te trays two 
inches square, and half an inch in depth, and the tem- 
perature ascertained by a delicate thermometer. 

Nothing can be more evident than that the genial 
heat of the soil, particularly in spring must be of the 
highest importance to the rising plant. And when the 
leaves are fully developed, the ground is shaded, and 
any injurious influence^ which in the summer might be 
expected from too great a hea^ entirely pteteuted ; so 



LECTtTEB IV. 

that the tempentnre of the sur&ce, when bare and 
exposed to the rays of the sun^ affords at least one indi* 
cation of the degrees of its fertility ; and the thermo- 
meter may be sometimes a useful instrument to the 
purchaser or impitiver of lands. 

There is a very simple test of the cooling or radiating 
powers of soils, the formation of dew upon them, or 
their reUtive increase of wei^t by exposure to the air 
after beisg dried, in the day or the night, in sunshine 
or in shade. The soil that radiates most heat acquires 
the greatest increase of we%ht: and of course the ra- 
diating powers of the soil are not only connected with 
its temperature, but likewii^ with its rekti^ms to mois- 
ture. 

The moisture in the soil influences its temperature ; 
and jthe manner in which it is liiatributed through, or 
combined with, the eartixy imatenals, is of great import- 
ance in relation to the nutriment of the plant. If 
water is too stron^y attractcfd by the eai^ths, it wijl not 
be absorbed by the roots of the plants ; if it is in too 
great quwtity, or too loosely united to them, it tends 
to injure or destroy tiie Sixous parts of the roots. 

There. are >two states m which water seems to exist in 
the .earAs, and in . animal and ii«getable substances : in 
the first state it is united by chemical, in the other by 
cohesive, attraction. 

If.pYU« solution jof. ammonia «r potassa.be poured 
into a solution of ali^m^ Alumina falls dfmA combined 
with water ; .-and the powder .dried by exposure to air 
willaffiird more .than half its weight of water by distil- 
lation; in. this [instance die.water:i9 uhitedbyichemicd 
attraction. The moistnre which wood, or muscular 
fibre, or gum, that have been, heated, to 212% afford by 
distiUatiop at a, red. heat,, is likewise . wiUer, the elements 



324 AGRICULTURAL CHEMISTRY. 

of which were united in the substance by diemical 
combination. 

When pipe-clay dried at the temperature of the at- 
mosphere is brought in contact with water, the fluid is 
rapidly absorbed : this is owing to cohesive attraction. 
Soils in general, vegetable and animal substances, that 
have been dried at a heat below that of boiling water, 
increase in weight by exposure to air, owing to their 
absorbing water existing in the state of vapour in the 
air, in consequence of cohesive attraction. 

The water chemicaUy combined amongst the elements 
of soils, unless in the case of the decomposition of ani- 
mal or vegetable substances, cannot be absorbed by the 
roots of plants ; but that adhering to the parts of the 
soil is in constant use in vegetation. Indeed, there are 
few mixtures of the earths found in soils that contain 
any chemically combined water; water is expelled from 
the earths by most substances that combine with them. 
Thus, if a combination of lime and water be exposed to 
carbonic acid, the carbonic acid takes the place of 
water ; and compounds of alumina and silica, or other 
compounds of the earths, do not chemically unite with 
water ; and soils, as it has been stated, are formed either 
by earthy carbonates, or compounds of the pure earths 
and metallic oxides. 

When saline substances exist in soils, they may be 
united to water both chemically and mechanically; but 
they are always in too small a quantity to influence 
materially the relations of the soil to water. 

The power of the soil to absorb water by cohesive 
attraction depends in great measure upon the state of 
division of its parts ; the more divided they are, the 
greater is their absorbent power. The different con- 
stituent parts of soils likewise appear to act, even by 



LBCTURB IV. 325 

cohesive attraction^ with different degrees of enei^* 
Thus vegetable substances seem to be more absorbent 
than animal substances; animal substances more so 
than compounds of alumina and silica ; and compounds 
of alumina and silica more absorbent than carbonates of 
lime and magnesia: these differences may, however, 
possibly depend upon the differences in their state of 
division, and upon the surface exposed. 

The power of soils to absorb water from air is much 
connected with fertility. When this power is great, 
the plant is supplied with moisture in dry seasons ; and 
the effect of evaporation in the day is counteracted by 
the absorption of aqueous vapour from the atmosphere, 
by the interior parts of the soil during the day, and by 
both the exterior and interior during the night. 

The stiff clays approaching to pipe-clays in their 
nature, which take up the greatest quantity of water 
when it is poured upon them in a fluid form, are not 
the soils which absorb most moisture from the atmo- 
sphere in dry weather. They cake, and present only a 
small surface to the air ; and the vegetation on them is 
generally burnt up almost as readily as on sands. 

The soils that are most efficient in supplying the 
plant with water by atmospheric absorption are those in 
which there is a due mixture of sand, finely divided 
clay, and carbonate of lime, with some animal or vege- 
table matter ; and which are so loose and light as to be 
freely permeable to the atmosphere. With respect to 
this quality, carbonate of lime and animal and vegetable 
matter are of great use in soils ; they give absorbent 
power to the soil without giving it likewise tenacity: 
sand, which also destroys tenacity, on the contrary, 
gives little absorbent power. 

I have compared the absorbent powers of many soils 



826 AGRICULTUEAL CHEMISTRY. 

with respect to atmoBpheric mdature, aiid I have always 
fimnd it greatest in the most £ertile soils; so that it 
affords one method of judging of the productiveneas of 
land. 

1000 parts of a celebrated soil £:om Qnniatown, in 
East Lothian, which contiuned more than half its we^t 
of finely divided matter, of which 11 parts were car- 
bonate of lime and 9 parts v^etable matter, when dried 
at 212^5 gained in an hour by exposure to air saturated 
with mmsture, at temperature 62°, 18 grains. 

1000 parts of a very fertile acdl ^om the banks of the 
river Parrec, in Somersetshire, under the same cirecmi- 
stances, gained 16 grains. 

1000 parts of a soil firom Mersea, in Essex, worth 45 
shillings an acre, guned 13 grains. 

1000 grains of a fine sand firom Essex, worth 28 shil- 
lings an acre, gained 11 grains. 

1000 of a coarse sand, worth 15 ahiUings an jacce, 
gained only 8 grains. 

1000 of the soil of Bagshot Heath, gained oaaJj 3 
grains. 

Water, and the decomposing animal and vegetable 
matter ensting in the. soil, constitute the true nourish- 
ment of plants; and as the earthy parts of the soil are 
usefiil in retaining water, so as to supply it in the proper 
proportions to the roots of the vegetables, jbo. they are 
likewise efficacious in producing the proper distributicm 
of the animal or vegetable matter : when equally mixed 
with it, they prevent it firom decomposing too rapidly ; 
and by their means the soluble parts are supplied in 
proper proportions. 

Besides this, agency, which may be cansidered as 
mechanical, there is another i^ency bdtwcbn^&oils and 
organizable matters, which may be regarded as chemical 



LECTUHB IT. 827 

in its nature. The earths, and even the earthy car- 
bonates^ have a certain degree of ehemieal attraction 
for many of the principles of vegetable and animal 
substances. This is easily exemplified in the instance 
of alumina and oil; if an acid solution of idmnina 
be mixed with a solution of soap, "which ccmsSsts of 
oily matter and potassa, the oil and the ahimina wall 
unite and form a white powder, which will sink to the 
bottom of the fluid. 

The extract from decomposing vegetable matter, 
when boiled with pipe-clay or chalk, forms a combina- 
tion by which the vegetable matter is rendered moi« 
difficult of decomposition and of solutioii. Pure 
silica and siliceous sands have little action of this kind; 
and the soils which contain the most alumina and car- 
bonate of lime are those which act with the greatest 
chemical energy in preserving manures. Such soils 
merit the appellation which is commonly given to them 
of rich soils ; for the vegetable nonnsfament is long 
preserved in them, unless taken up by the organs of 
plants. Siliceous sands, on the contrary, deserve 
the term hungry, which is commonly applied to them, 
for the vegetable and animal matters they contain 
not being attracted by the earthy constituent parts 
of the soil, are more liable to be decomposed by the 
action of the atmosphere, or carried off firom them by 
water. 

In most of the blade and brown vegetable moulds, 
the earth seems to be in combination with a peculiar 
extractive matter, afforded during the decomposition of 
vegetables : this is slowly taken up, or attracted from 
the earths by water, and appears to con^itute a prime 
cause of the fertility of the soil. 

The standard of fertility of soils for different plants 



328 AGRICULTURAL CHEMISTRY. 

must vary with the climate ; and must be particularly 
influenced by the quantity of rain. 

The power of soils to absorb moisture ought to be 
much greater in warm or dry countries than in cold or 
moist ones ; and the quantity of clay^ or vegetable or 
animal matter they contain, greater. Soils also on 
declivities ought to be more absorbent than in plains or 
in the bottom of valleys. Their productiveness like- 
wise is influenced by the nature of the sub-soil or the 
stratum on which they rest 

When soils are immediately situated upon a bed 
of rock or stone, they are much sooner rendered dry by 
evaporation, than where the sub-soil is of clay or marl ; 
and one cause of the great fertility of some lands in 
the moist climate of Ireland is the proximity of the 
rocky strata to the soil. 

A clayey sub-soil will sometimes be of material ad- 
vantage to a sandy soil ; and in this case it will retain 
moisture in such a manner as to be capable of supply- 
ing that lost by the earth above, in consequence of 
evaporation, or the consumption of it by plants. 

A sandy or graveUy sub-soil often corrects the im- 
perfections of too great a degree of absorbent power in 
the true soil. 

In calcareous countries, where the surface is a species 
of marl, the soil is often found only a few inches above 
the limestone ; and its fertility is not impaired by the 
proximity of the rock : though in a less absorbent soil^ 
this situation would occasion barrenness ; and the sand- 
stone and limestone hills in Derbyshire and North 
Wales may be easily distinguished at a distance in sum« 
mer by the different tints of the vegetation. The grass 
on the sandstone hills usually appears brown and burnt 
up ; that on the limestone hills, flourishing and green. 



LECTURE IV. 329 

In devoting the different parts of an estate to the 
necessary crops^ it is perfectly evident from what has 
been said that no general principle can be laid down^ 
except when all the circumstances of the nature^ com* 
position^ and situation of the soil and sub-soil are 
known. 

The methods of cultivation likewise must be different 
for different soils. The same practice which will be 
excellent in one case may be destructive in another. 

Deep ploughing may be a very profitable practice in 
a rich thick soil ; and in a fertile shallow soil, situated 
upon cold clay or sandy suhnsoil^ it may be extremely 
prejudicial. 

In a moist climate where the quantity of rain that 
falls annually equals from 40 to 60 inches, as in 
Lancashire, Cornwall, and some parts of Ireland, 
a siliceous sandy soil is much more productive than in 
dry districts ; and in such situations, wheat and beans 
will require a less coherent and absorbent soil than in 
drier situations ; and plants having bulbous roots will 
flourish in a soil containing as much as 14 parts out of 
15 of sand. 

Even the exhausting powers of crops will be in- 
fluenced by like circumstances. In cases where plants 
cannot absorb sufficient moisture, they must take up 
more manure. And in Ireland, Cornwall, and the 
Western Highlands of Scotland, com will exhaust less 
than in dry inland situations. Oats, particularly in 
dry climates, are impoverishing in a much higher degree 
than in moist ones. 

Soils appear to have been originally produced in 
consequence of the decomposition of rocks and strata. 
It often happens, that soils are found in an unaltered 
state upon the rocks from which they were derived. 



330 AGRICULTURAL CHEMISTRY. 

It IS easjr to form an idea of die manner in which rocks 
are converted into soils, bjr referring to the instance of 
sqft graniU or ptm^dam grcaate. This substance coiuastB 
of three ingredients, quartz, feldspar, and mica. The 
quarts is ahnost pure siliceous earth, in a cijstamiie 
form. The feldspar and mica are very compoonded 
substances; both contain silica, alumina, and oxide 
of iron: in the feldspar there is usually lime and 
potassa ; in ihe mica, lime and magnesia. 

When a granitic rock of this kind has been long 
exposed to the influence of air and water, the lima 
and the potassa contained in its constituent psrti 
are acted upon by water or carbonic acid; and the 
oxide of iron, which is almost always in its least 
oxided state, tends to combine with more oi^gen; 
the consequence is, that the feldspar decomposes, and 
likewise the micsy but the first the most rapidly. The 
feldspar, which is as it were the cemesit of the stone, 
forms a fine clay ; the mica partially decomposed mixes 
with it as sand; and the undecompoeed quartz appears 
as gravel, or sand of different degrees of fineness. 

As soon as the smallest layer of earth is formed on 
the surface of a rock, the seeds of lichenai, mosses;, 
and other iraperfoct vegetables which are constantly 
floating in the atmosphere ; and which have made 
it their resting-place, begin to vegetate : their death, 
decomposition, and decay, afibrd a certain quantity 
of organlzable matter, which mixes with the earthy 
materials of the rock; in this improved soil more 
perfect plants are capable of subsisting; th^e in 
their turn absorb nourishment firom water and the 
atmosphere ; and after perishing, afibrd new materials 
to those already provided : the decomposition of the 
rock still continues ; and at lei^h, by such dpw and 



LECTURB IV. 331 

gradual processeSi a soil is formed in which even forest 
trees can fix their roots, and which is fitted to reward 
the labours of the cultivator. 

In instances where successive generations of vege- 
tables have grown upon a soil^ unless part of their 
produce has been carried off by man, or consumed 
by animals, the vegetable matter increases in such 
a proportion that the soil approaches to a peat in 
its nature ; and if in a situation where it can receive 
water from a higher district, it becomes spongy, and 
permeated with that fluid, and is gradnally rendered 
incapable of supporting the nobler classes of vegetables* 

Many peat-mosses seem to have been formed by the 
destruction of forests, in consequence of the imprudent 
use of the hatchet by the early cultivators of the 
country in which they e^tist : when the trees are felled 
in the outskirts of a wood^ those in the interior, exposed 
to the influence of the winds, and having been ae* 
customed tb shelter, become unhealthy, and die in their 
new situation ; and their leaves and branches gradually 
decomposing, produce a stratum of vegetable matter. 
In many 6f the great bogs in Ireland and Scotland, the 
k^ger trees that are found in die outskirts of tbem bear 
the marks of haviiig been felled. In the interior few 
entire trees are found ; and the cause is, probably, that 
they fell by gradual decay ; and that the fermentation 
and decomposition of the vegetable matter was most 
rapid where it was in the greatest quantity. 

Lakes Mid pools of water are sometimes filled up by 
the accumulation of the remains of aquatic plants ; and 
in this case a sort of spurious peat is formed. The fer* 
mentation in these cases, however, seems to be of a 
different kind. Much more gaseous matter is evolved ; 
and the neighbourhood of morasses in which aquatic 



332 AGRICULTURAL CHBMISTRY. 

vegetables decompoee is usually aguish and unhealthy; 
whilst that of the true peat, or peat formed on soils 
originally dry, is always salubrious. 

The earthy matter of peats is uniformly analogous to 
that of the stratum on which they repose ; the plants 
which have formed them, must have derived the earths 
that they contained from this stratum. Thus, in Wilt- 
shire and Berkshire, where the stratum below the peat 
is chalk, calcareous earth abounds in the aahes, and veiy 
little alumina and silica. They likewise contain much 
oxide of iron and gypsum, both of which may be derived 
from the decomposition of the pyrites, so abundant in 
chalk. 

Different specimens of peat that I have burnt fit>m 
the granitic and schistose soils of different parts of these 
islands, have always given ashes, principally siliceous 
and aluminous; and a specimen of peat from the county 
of Antrim, gave ashes which afforded very nearly the 
same constituents as the great basaltic stratum of the 
county. 

Poor and hungry soils, such as are produced from the 
decomposition of granitic and sandstone rocks, remain 
very often for ages with only a thin covering of vegeta- 
tion. Soils from the decomposition of limestone, chalks, 
and basalts, are often clothed by nature with the peren- 
nial grasses ; and afford, when ploughed up, a rich bed 
for the vegetation of every species of cultivated plant. 

Rocks and strata, from which soils have been derived, 
and those which compose the more interior solid parts 
of the globe, are arranged in a certain order; and as it 
often happens that strata very different in their nature 
are associated together, and that the strata immediately 
beneath the soil contain materials which may be of use 
for improving it, a general view of the nature and posi-> 



LECTURE IV. 333 

tion of rocks and strata in nature, will not, I trust, be 
unacceptable to the scientific fiurmer. 

Rocks are generally divided by geologists into two 
grand divisions, distinguished by the names of primanf 
and secondary. 

The primary rocks are composed of pure crystalling 
matter, and contain no fragments of other rocks. 

The secondary rocks, or strata, consist only partly of 
crystalline matter, contain fragments of other rocks or 
strata; oflen abound in remains of vegetables and marine 
animals; and sometimes contain the remains of land 
animals. 

The primary rocks are generally arranged in laige 
masses, or in layers, vertical, or more or less inclined to 
the horizon. 

The secondary rocks are usually disposed in strata or 
layers, parallel, or nearly parallel, to the horizon. 

The number of primary rocks which are commonly 
observed in nature, are eight 

First, granite^ which, as has been mentioned, is com- 
posed of quartz, feldspar, and mica ; when these bodies 
are arranged in regular layers in the rock, it is called 
gneis. 

Second, micaceous schistiis, which is composed of quartz 
and mica, arranged in layers, which are usually curvi- 
lineal. 

Third, sienite, which consists of the substance caUed 
hornblende and feldspar. 

Fourth, serpentine, which is constituted by feldspar, 
and a body named resplendent hornblende ; and their 
separate crystals are often so small, as to give the stone 
a uniform appearance : this rock abounds in veins of a 
substance called steatite, or saajhrocK 

FifUi, porphyry y which consists of crystals of feldspfu*, 



884 AGRICULttrBAL OfiBHISTRT. 

•mbedded in the flame material^ bat usually of a dif- 
ferent colour. 

Sixth, granufar marble^ which consifitB entirely of ciys- 
t^la of carbonate of lime ; and which, when its colour is 
white, and texture fine, is the substance used by sta- 
fuartes. 

Seventh, chhrite sokUti which consists of dblorite, a 
ffe^ or gvey tabBtaQCe, somewhat analogous to mica 
Aadfelds|>ar. 

Eighdi, gttarUMe roeky which is c(»nposed of quartz 
ma granular form, sometimes united to small quantities 
of the crystalline elements, which have been mentioned 
as belonging to the other rocks. 

Hie aeoondary rocks are more numerous than the 
primary ; but twelve varieties include all that are usually 
found in these islimds. 

First, fftautbaehe, which consists of fragments of 
qutti^ or dblorite schist, embedded in a cement, prin- 
cipally composed of feldspar. 

Secend, ^£Hieou$ siaAtaHey which is composed of fine 
quatts' or aand, unit^ by a sSiceOus cemebt 

Third, Kmestaney consisting of carbonate of time, more 
compact in its texture, than in the granular marble ^ and 
often abounding in marine eJtuvise. 

Fourth, 4duininous schist or ^juzk^ consisting of the de- 
composed materials of different rocks, cemented by a 
small quantity of ferruginous or siliceous matter; and 
often containing the impressions of vegetables. 

S^h, caieareaus stmdst&ne, whicfh is calcareous sand^ 
cemented by cak)areOus matter. 

SLitlh, ironstone, fonked of ilearly the same materials 
as aluininous «chist 6r -shale ; but ^ontaiiuitig a much 
larger quantity of oxidet>f iDon. 

Seventh, tostfiZ^ or taAmlbne, which cansists of feld- 



LECTUBB IT. 335 

spar and hornblende, with materials derived from the 
decomposition of the primary rocks ; the crystals are go** 
nerally so small, as to giye the rock a homogeneons ap- 
pearance ; and it is often disposed in very i«gular co- 
lumns, haying usually five or six sides. 

Eighth, bituminous or covnimon eooL 

Ninth, ffypsum, the substance so well known by diat 
name, which consists of sulphate of Ume ; and often ccfs^ 
tains sand. 

Tenth, rock salt. 

Eleventh, chalk, whidi usually abounds in remains 
of mariae animelcf, and contains horizontal layers of 
flints. 

Twelfth, phtm-puddinff stone, consisting x>f pebUeB 
cemented by a ferruginous or siliceous cement 

To describe more particularly the constituent parts 
of the different rocks and strata, will be unnecessary ; 
at any time, indeed^ details on this subject are useless, 
unless the specimens are examined by the eye; and a 
dose ixispection and comparison of the di&rent q>ecie6, 
will, in a short time, enable the most common observer 
to distinguidi th^m. 

The highest mountains in these islands, and, indeed^ 
lai the whole of the old continent, are constituted by grar 
Qite ; and this rock has likewise been found at the greatest 
depths to which the industry of man has as yet been 
able to .penetrate ; micaceous schist is often found imme* 
diately upon granite ; serpentine or marble upon mica-' 
cebiis schist; but thie order in which the primary rocks 
ase grouped together, is various. Marble and serpen- 
tine are usually found uppermost ; but granite, though 
it seems to form the foundation of the rocky strata vi 
the gbbe, .is yet sometimes discovered above micaoecfu^ 
schist. 



336 AORICULTCRAL CHEMISTRT. 

The flecondaiy rocks axe always incambent on the 
primaiy; the lowestof themis nsaallygniawacke; apoa 
this limestone or sandstone is often fixind; coal genenBy 
oocais between sandstone or shale : basalt often exists 
above sandstone and limestone ; rock-6alt almost always 
occois associated with red sandstone and gypeom. 
Coal, basalt, sandstone, and limestone, are ofbai 
arranged in different alternate layers, of no considerable 
thicknessy so as to form a great extent of countiy. In 
a depth of less than 500 yards, 80 of these different 
alternate strata have been counted. 

The veins which afford metallic snbstances, aie fis- 
sures vertical, or more or less inclined, filled with a ma- 
terial different fix>m the rock in which they exist This 
material is almost always crystalline ; and usually con* 
sists of calcareous spar, fluor spar, quartz, or heavy spar, 
either separate or together. The metallic substances 
are generally dispersed through, or confiisedly mixed, 
with these crystalline bodies. The veins in hard gra- 
nite, seldom afford much usefiil metal ; but in the veins 
in soft granite, and in gneis, tin, copper, and lead are 
found. Copper and iron are the only metals usually 
found in the veins in serpentine. Micaceous schist, 
sienite, and granular marble, are seldom metalliferous 
rocks. Lead^ tin, copper, iron, and many other metab, 
are found in the veins in chlorite schist. Grauwacke, 
when it contains few firagments, and exists in large 
masses, is often a metalliferous rock. The precious 
metals, likewise iron, lead, and antimony, are found in 
it ; and sometimes it contains veins, or masses of stone 
coal, or coal fiee firom bitumen. Limestone is the great 
metalliferous rock of the secondary family ; and lead and 
copper are the metals most usually found in it. No me- 
tallic veins have ever been found in shale, chalk, or cal- 



A -. 







LECTURE IV. -337 

ireous sandstone ; and they are very rare in basalt and 
iiceous sandstone.* 

In cases where veins in rocks are exposed to the at- 
Qosphercy indications of the metals they contain may be 
>ften gained^ from their superficial appearance. When- 
ever fluor spar is found in a vein, there is always strong 
^.^"eason to suspect that it is associated with metallic sub- 
stances. A brown powder at the surface of a vein^ 
always indicates iron, and often tin; a pale yellow 
powder, lead; and a green colour in a vein, denotes the 
presence of copper. 

It may not be improper to give a general description 
of the geological constitution of Great Britain and Ire- 
land. Granite forms the great ridge of hills extending 
from Land's End through Dartmore into Devonshire. 
The highest rocky strata in Somersetshire are grau- 
wacke and limestone. The Malvern hills are composed 
of granite, sienite, and porphyry. The highest moun- 
tains in Wales are chlorite schist, or grauwacke. Gra- 
nite occurs at Mount Sorrel, in Leicestershire. The 
great range of the mountains in Cumberland, and 
Westmoreland are porphyry, chlorite, schist and grau- 
wacke ; but granite is found as their western boundary. 
Throughout Scotland the most elevated rocks are gra- 
nite^ sienite, and micaceous schistus. No true secondary 
formations are found in South Britain, west of Dart- 
more ; and no basalt south of the Severn. The chalk 
district extends from the western part of Dorsetshire to 
the eastern coast of Norfolk. The coal formations 
abound in the district between Glamorganshire and 
Derbyshire; and likewise in the secondary strata of 
Yorkshire, Durham, Westmoreland, and Northumber- 

^ Fig. 16. will give a general idea of the appearance and arrangement 
of rocks and veins. 

VOL. vn. Q 



338 AGRICULTUHAL CHEMISTRY. 

land. Serpentine is foond only in three pliuses in 
Great Britain ; near Cape Lizard in Cornwall, Portsoy 
in Aberdeenshire, aond in Ayrshire. Black and grey 
granular marble is found near Padstow in Comvall; 
and other coloured primary marbles exist in the neigh- 
bourhood of Plymouth. Coloured primary marbles aie 
abundant in Scotland; and white granular marble is 
found in the Isle of Sky, in Assynt, and on the banks 
of Loch Shin in Sutherland : the principal coal forma- 
tions in Scotland are in Dumbartonshire, Ayrshire, Fife- 
shire, and on the banks of the Brora, in Sutherland. 
Secondary limestone and sandstone are found in most 
of the low countries north of the Mendip hills. 

In Ireland there are five great associations of primary 
mountains ; the mountains of Mome, in the county <^ 
Down ; the mountains of Donegal ; those of Mayo and 
Galway ; those of Wicklow ; and those of Kerry. The 
rocks composing the four first of these mountain chains 
are principally granite, gneis, sienite, micaceous schist, 
and porphyry. The mountains of Ketry are chiefly 
constituted by granular quartz, and chlorite schist. 
Coloured marble is found near Killamey; and white 
marble on the western coast of Donegal. 

Limestone and sandstone are the common secondaiy 
rocks found south of Dublin. In Sligo, Roscommon, 
and Leitrim, limestone, sandstone, shale, ironstone, and 
bituminous coal are found. The secondaiy hills in 
these counties are of considerable elevation; and many 
of them have basaltic summits. The north coast of 
Ireland is principally basalt; this rock commonly re* 
poses upon a white limestone, containing layers of flint, 
and the same fossils as chalk; but it is considerably 
harder than that rock. There are some instances, in 
this district, in which columnar basalt is found above 



I^CTURE IV. 339 

sandstone and shale^ altematiBg widi <;oaL The stone- 
coal of Ireland is principallj found in Kilkenny, as- 
sociated with limestone and grauwacke. 

It is evident fix>m what has beeai said concerning the 
production of soils from rocks, that there must be at 
least as many varieties of soils as there are species of 
rocks exposed at the surface of the earth ; in fact there 
are many more. Independent of the changes produced 
by cultivation and the exertions of human labour, the 
materials of strata have been mixed together and trans- 
ported from place to place by various great alterations 
that have taken place in the system of our globe, and 
by the constant operation of water. 

To attempt to class soils with scientific accuracy would 
be a vain labour; the distinctions adopted by &rmers 
are sufficient for the purposes of agriculture ; par- 
ticularly if some degree of precision be adopted in the 
application of terms. The term sandy, for instance, 
should never be applied to any soil that does not con- 
tain at least ^ of Sand ; sandy soils that efiervesce with 
acids should be distinguished .by the name of calcareous 
sandy soil, to distinguish them from those that are sili- 
ceous. The term clayey soil should not be applied to 
any land which contains less than ^ of impalpable earthy 
matter, not considerably effsnrescing with acids: the 
word loam should be limited to soils containing at 
least one-third of impalpable earthy matter, copiously 
effervescing with acids. A soil, to be considered as 
peaty, ought to contain at least one-half of vegetable 
matter. 

In cases where the earthy part of a soil evidently 
consists of a decomposed matter of one particular rock, 
a name derived from the rock may with propriety be 
applied ,to it Thus, if a fine xed earth be found im- 

q2 



340 AGBICULTURAL CHEMISTRY. 

mediately above decomposiDg basalt, it may be denomi- 
nated basaltic soil If fragments of quartz and mics 
be found abundant in the materials of the soil^ which 
is often the case, it may be denominated granitic soil ; 
and the same principles may be applied to other like 
instances. 

In general, the soils, the materials of which are the 
most various and heterogeneous, are those called al- 
luvial, or which have been formed from the depositions 
of rivers ; many of them are extremely fertile. I have 
examined some productive alluvial soils, which have 
been very different in their composition. The soil 
which has been mentioned page 326 as very productive, 
from the banks of the river Parret in Somersetshire, 
afforded me eight parts of finely divided earthy matter, 
and one part of siliceous sand ; and an analysis of the 
finely divided matter gave the following results: — 

360 parts of carbonate of lime. 
25 — alumina. 
20 — silica. 
8 — oxide of iron. 
19 — vegetable, animal, and saline matter. 

A rich soil from the neighbourhood of the Avon^ in 
the valley of Evesham in Worcestershire, afforded me 
three-fifths of fine sand^ and two-fifths of impalpable 
matter ; the impalpable matter consisted o^ 

35 Alumina. 

41 SiUca. 

14 Carbonate of lime. 

3 Oxide of iron. 

7 Vegetable, animal, and saline matter. 

A specimen of good soil from Tiviot-dale^ afforded 



LSCTURE rv. 341 

five-sixths of fine siliceous sanely and one-sixth of im- 
palpable matter; which consisted of 

41 Alumina. 

42 SiUca. 

4 Carbonate of lime. 

5 Oxide of iron. 

8 Vegetable^ animal^ and saline matter. 
A soil yielding excellent pasture firom the valley 
of the Avon, near Salisbury, afibrded one-eleventh of 
coarse siliceous sand; and the finely divided matter 
consisted of 

7 Alumina. 
14 Silica. 

63 Carbonate of lime. 
2 Oxide of iron. 

14 Vegetable, animal, and saline matter. 
In all these instances the fertility seems to depend 
upon the state of division, and mixture of the earthy 
materials and the vegetable and animal matter; and 
may be easily explained on the principles which I have 
endeavoured to elucidate in the preceding part of this 
Lecture. 

In ascertaining the composition of sterile soils with 
a view to their improvement, any particular ingredient 
which is the cause of their unproductiveness, should be 
particularly attended to; if possible, they should be 
compared with fertile soils in the same neighbourhood, 
and in similar situations, as the difierence of the com- 
position may, in many oases, indicate the most proper 
methods of improvement If on washing a sterile soil 
it is found to contain the salt of iron, or any acid 
matter, it may be ameliorated by the application of 
quicklime. A soil of good apparent texture firom Lin- 
colnshire, was put into my hands by Sir Joseph Banks 



342 AGRICULTURAL CHEMISTRY. 

as remafkable for sterility. On examining it» I foimd 
that it contained suipliate of iron ; and I offered the 
obvious remedy of top-dressing Ttrith Hme, which con- 
verts the sulphate into a manure. If there be an excess 
of calcareous matter in the soil, it may be improved by 
the application of sand, or clay. Soils too abundant in 
sand are benefited by tbe use of clay or marl, or vege- 
table matter. A field belonging to Sir Robert Yaughan 
at Nannan, Merionethshire^ the soil of which vras a 
tight sand, was much burnt up in the summer of 1806 ; 
I recommended to that gentleman the application of peat 
as a top-dressing. The experiment was attended with 
immediate good effects ; and Sir Robert has informed 
me, that the benefit was permanent. A deficiency of 
vegetable or animal matter must be applied by manure. 
An excess of vegetable matter is to be removed by 
burning, or to be remedied by the application of earthy 
materials. The improvement of peats, or bogs, or maisli 
lands, must be preceded by draining; stagnant water 
being injurious to all the nutritive classes of plants. 
Soft black peats, when drained, are often made pro« 
ductive by the mere application of sand or clay as a 
top-dressing. When peats are add, or contain ferru- 
ginous salts, calcareous matter is absolutely necessary 
in bringing them into cultivation. When they abound 
in the branches and roots of trees, or when their surface 
entirely consists of living vegetables, the wood or the 
vegetables must either be carried off, or be destroyed 
by burning. In the last case their ashes afford 
earthy ingredients, fitted to improve the texture of the 
peat. 

The best natural soils are those of which the materials 
have been derived from different -strata; which have 
been minutely divided by air and water, and are inti. 



I^ECTUBB IV. 343 

mately blended together; and in improving soils artifi- 
ciallj, the fEunoaer cannot do better than imitate the 
processes of nature. 

The materials necessary for the purpose are seldom 
far distant : coarse sand is often found immediately on 
chalk ; and beds of sand and gravel are common below 
day. The labour of improving the texture or constitu- 
tion of the soil is repaid by a great permanent advan- 
tage ; less manure is required, and its fertility insured. 
And capital laid out in this way secures, for ever, the 
productiveness, and consequently the value, of the land. 



344 AGRICULTURAL CHBMI6TRT. 



LSCTURE V. 

On the Nature and Constitation of the Atmosphere, and its Influence on 
YegetebleB.— Of the Qermination of Seeds. -—Of the Fimctiona d 
Plants in their diiBferent Stages of Growth; with a Gcaenl View of 
the Progress of Vegetation. 

The constitution of the atmosphere has been abeady 
generally referred to in the preceding Lectures. Water, 
carbonic acid gas, oxygen, and azote, have been men- 
tioned as the principal substances composing it; but 
more minute inquiries respecting their nature and 
agencies, are necessary to afford correct views of the 
uses of the atmosphere in vegetation. 

On these inquiries I now propose to enter ; the pur- 
suit of them, I hope, will offer some objects of practical 
use in fiurming; and present some philosophical illustra- 
tions of the manner in which plants are nourished, their 
oi^ns unfolded, and their functions developed 

If some of the salt, called muriate of lime, that has 
been just heated red, be exposed to the air, even in the 
driest and coldest weather, it will increase in weight, 
and become moist ; and, in a certain time, will be con- 
verted into a fluid. If put into a retort and heated, it 
will yield pure water ; will gradually recover its pristine 
state ; and, if heated red, its former weight: so that it 
is evident that the water united to it was derived from 
the air. And that it existed in the air in an invisible 
and elastic form, is proved by the circumstance, that if 
a given quantity of air be exposed to the salt, its volume 



LECTURE V. 345 

and weight will diminish, provided the experiment be 
correctly made. 

The quantity of water which exists in air, as vapour, 
varies with the temperature. In proportion as the 
weather is hotter, the quantity is greater. 

At 50^ of Fahrenheit, air contains about ^ of its vo- 
lume of vapour; and as the specific gravity of vapour 
is to that of air nearly as 10 to 15, this is about -^ of 
its weight. 

At 100®, supposing that there is a firee communication 
with water, it contains about -j^ part in volume, or ^ 
in weight It is the condensation of vapour by diminu- 
. tion of the temperature of the atmosphere, which is pro- 
bably the principal cause of the fonnation of clouds, and 
of the deposition of dew, mist, snow, or haiL 

The power of difierent substances to absorb aqueous 
vapours from the atmosphere, by cohesive attraction, was 
discussed in the last Lecture. The leaves of living 
plants appear to act upon the vapour, likewise, in its 
elastic form, and to absorb it. Some vegetables increase 
in weight fi*om this cause, when suspended in the at- 
mosphere, and unconnected with the soil ; such are the 
houseleek, and different species of the aloe. In very 
intense heats, and when the soil is dry, the life of plants 
seems to be preserved by the absorbent power of their 
leaves : and it is a beautiM circumstance in the eco- 
nomy of nature, that aqueous vapour is most abundant 
in the atmosphere when it is most needed for the pur- 
pose of life ; and that when other sources of its supply 
are cut off, this is most copious. 

The compound nature of water has been referred to. 
It may be proper to mention the experimental proofs of 
its decomposition into, and composition from, oxygen, 
and hydrogen. 

q6 



346 AGRICULT17RAL CHBMISTRT. 

If the metal called potassium be exposed in a glafl0 
tube to a small quantity of water^ it will act upoa it 
with g^at violence; elastic fluid will be disengaged^ 
which will be found to be hydrogen; and the same 
effects will be produced upon llie potassium as if it had 
absorbed a small quantity of oxygen ; and the hydrogen 
disengaged, and the oxygen added to the potassiam^ 
are in weight as 2 to 16 ; and if two in volume of by- 
drogen, and one in volume of oxygen, which have the 
weights of 2 and 15, be introduced into a close vessel, 
and an electrical spark passed through them, they will 
inflame and condense into 17 parts of pure water. 

It is evident from the statements given in the third 
Lecture, that water forms by tar the greatest part of 
the sap of plants ; and that this substance, or its ele- 
ments, enters laigely into the constitution of their oxgans 
and solid productions. 

Water is absolutely necessary to the economy of ve- 
getation in its elastic and fluid state; and it is not 
devoid of use even in its solid form. Snow and ice are 
bad conductors of heat ; and when the ground is covered 
with snow, or the sur&ce of the soil or of water is 
frozen, the roots or bulbs of the plants beneath are pro* 
tected by the congealed water from the influence of the 
atmosphere, the temperature of which in northern win- 
ters is usually very much below the freezing point; and 
this water becomes the flrst nourishment of the plant 
in early spring. The expansion of water during its 
congelation, at which time its volume increases -j^, and 
its contraction of bulk during a thaw, tend to pulverise 
the SOU ; to separate its parts from each other, and to 
make it more permeable to the influence of the air. 

If a solution of lime in water be exposed to the air, 
a pellicle will speedily form upon it, and a solid matter 



LBonrBX Y. 34t 

will gradually fUl to the bottom of tbe water> and in a 
certain time the water will become tasteless; this is 
owing to the combination of the lime, which was difr- 
solved in the water with carbonic acid gas which existed 
in the atmosphere, as may be proved by collecting tbe 
film and the solid matter, and igniting them strcMigly in 
a little tube of platina or iron : they will give off car- 
bonic add gas, and will become quicklime, which, added 
to the same water, will again bring it to the state of 
lime-water. 

The quantity of carbonic acid gas in the atmosphere 
is very smalL It is not easy to determine it with pre* 
cision, and it must differ in different situations; but 
where there is a firee circulation of air, it is probably 
never more than -^^ nor less than -^ of the volume 
a( air. Carbonic acid gas is nearly ^ heavier than the 
other elastic parts of the atmosphere in their mixed 
state : hence, at first view^ it might be supposed that it 
would be most abundant in the lower regions of the 
atmosphere; but unless it has been immediately pro* 
duced at the surfiice of the earth in some chenucal pro- 
cess, this does iiot seem to be the case : elastic fluids of 
different specific gravities have a tendency to equable 
mixture by a species of attraction, and the different 
parts of the atmosphere are constantly agitated and 
blended together by winds or other causes. De Saus- 
sure found lime-water precipitated on Mount Blanc, 
the highest point of land in Europe ; and carbonic acid 
gas has been always found, apparently in due propor- 
tion, in the air brought down firom great heights in the 
atmosphere by aerostatic adventuren. 

The experimental proo& of the composition of car- 
bonic acid gas are very simple. If 13 grains of well 
burnt charcoal be inflamed by a buming-glafls in 100 



348 AGRICULTURAL CHSMISTRT. 

cubical inches of oxygen gas» the charcoal will entirely 
disappear; and» provided the experiment be correctly 
made, all the oxygen, except a few cubical inches, will 
be found converted into carbonic acid; and, what is 
very remarkable, the volume of the gas is not dianged. 
On this last circumstance it is easy to found a correct 
estimation of the quantity of pure charcoal and oxygen 
in carbonic acid gas : the weight of 100 cubical inches 
of carbonic acid gas is to that of 100 cubical inches of 
oxygen gas, as 47 to 34 : so that 47 parts in weight of 
carbonic acid gas must be composed of 34 parts of 
oxygen and 13 of charcoal, which correspond with the 
numbers given in the second Lecture* 

Carbonic acid is easily decomposed by heating potas- 
sium in it ; the metal combines with the oxygen, and 
the charcoal is deposited in the form of a black powder. 

The principal consumption of the carbonic acid in 
the atmosphere, seems to be in affording nourishment 
to plants ; and some of them appear to be supplied with 
carbon chiefly from this source. 

Carbonic acid gas is formed during fermentation, 
combustion, putre&ction, respiration, and a number of 
operations taking place upon the surfiice of the earth ; 
and there is no other process known in nature by which 
it can be destroyed but by vegetation. 

After a given portion of air has been deprived of 
aqueous vapour and carbonic acid gas, it appears little 
altered in its properties; it supports combustion and 
animal life. There are many modes of separating its 
principal constituents, oxygen, and azote, from each 
other. A simple one is by burning phosphorus in a 
confined volume of air : this absorbs the oxygen and 
leaves the azote; and 100 parts in volume of air in 
which phosphorus has been burnt, yield 79 parts of 



LBCTURB V. 349 

azote ; and by mixing this azote ^th 21 parts of fresh 
oxygen gas artificially procured^ a substance having the 
original characters of air is produced. To procure pure 
oxygen from air, quicksilver may be kept heated in it, 
at about GOO^, till it becomes a red powder : this pow- 
der, when ignited, will be restored to the state of quick- 
silver by giving off oxygen. 

Oxygen is necessary to some functions of vegetables, 
but its great importance in nature is in its relation to 
the economy of animals. It is absolutely necessary to 
their life. Atmospheric air taken into the lungs of 
animals, or passed in solution in wat^r through the gills 
of fishes, loses oxygen ; and for the oxygen lost, about 
an equal volume of carbonic acid appears. 

The effects of azote in vegetation are not distinctly 
known. As it is found in some of the products of 
vegetation, it may be absorbed by certain plants from 
the atmosphere. It prevents the action of oxygen from 
being too energetic, and serves as a medium in which 
the more essential parts of the air act : nor is this cir* 
cumstance unconformable to the analogy of nature ; for 
the elements most abundant on the solid sur&ce of the 
globe, are not those which are the most essential to the 
existence of the living beings belonging to it. 

The action of the atmosphere on plants differs at 
different periods of their growth, and varies with the 
various stages of the developement and decay of their 
organs. Some general idea of its influence may have 
been gained from circumstances already mentioned : I 
shall now refer to it more particularly, and endeavour 
to connect it with a general view of the progress of 
vegetation. 

If a healthy seed be moistened and exposed to air at 
a temperature not below 45^, it soon germinates; it 



350 AGRICULTI7BAL CHBMI8TRT. 

shoots forth a plume which riaes upwards, and a radicle 
which descends. 

If the ur be confined^ it is found that in the process 
of germination the oxygen, or a part of it, is absorbed. 
The azote remains unaltered ; no carbonic acid is taken 
away from the air ; on the contrary, some is added. 

Seeds are incapable of germinating, except when 
oxygen is present In the exhausted receiver of the 
air-pump, in pure azote, in pure carbonic acid, when 
moistened they swell, but do not vegetate ; and if kept 
in these gases, lose their living powers, and undergo 
putrefaction. 

If a seed be examined before germination, it will be 
found more or less insipid, at least not sweet ; but after 
germination it is always sweet Its coagulated muci- 
lage, or starch, is converted into sugar in the process ; 
a substance difficult of solution is changed into one 
easily soluble ; and the sugar carried through the cells 
or vessels of the cotyledons, is the nourishment of the 
infant plant It is easy to understand the nature of the 
change, by referring to the facts mentioned in the third 
Lecture ; and the production of carbonic acid rendeiB 
probable the idea, that the principal chemical difference 
between sugar and mucilage depends upon the sugar 
containing a laiger proportion of the elements of water, 
and upon a slight difference in the proportions of their 
carbon. 

The absorption of oxygen by the seed in germina^ 
lion, has been compared to its absorption in producing 
the evolution of foetal life in the egg; but this analogy 
is only remote. All animals, from the most to the least 
perfect classes, require a supply of oxygen.* From the 

* The impregfnated eggA of insects, and even of flsfaes, do not 
pvodnce young ones, unless they an supplied with air, that is. 



LECTURE Y. 351 

moment the heart begins to pukate till it ceases to beat, 
the aeration of the blood is constant, and the function 
of respiration invariable ; carbonic acid is given off in 
the process, but the chemical change produced in the 
blood is unknown ; nor is there any reason to suppose 
the formation of any substance similar to sugar. In 
the production of a plant from a seed, some reservoir 
of nourishment is needed before the root can supply 
sap ; and this reservoir is the cotyledon, in which it is 
stored up in an insoluble form, and protected, if neces* 
sary during the winter, and rendered soluble by agents 
which are constantly present on the surface. The 
change of starch into sugar, connected with the absorp- 
tion of oxygen, may be rather compared to a process of 
fermentation than to that of respiration ; it is a change 
effected upon unorganized matter, and can be artifici- 
ally imitated; and in most of the chemical changes 
that occur when vegetable compounda are exposed to « 
lur, oxygen is absorbed, and carbonic acid formed or 
evolved. 

unless the foetus can respire. I have foand that the eggs of moths 
did not produce larvee when confined in pure carbonic acid ; and when 
they were tzposed in common air, the oxygen partly disappeared, and 
carbonic acid was formed. The fish in the egg or spawn gains its 
oxygen from the air dissolved in water ; and those fishes that spawn in 
spring and summer in still water, such as pike, carp, perch and bream, 
deposit their eggs upon subaquatic yegetables, the leaves of which, in 
performing thetr healthy ftmetioos, supply oxygen to the water. The 
fish that spawn hi winter, such as salmon and trout, seek spots where 
there is a constant supply of fresh water, as near the sources of streams 
as possible, and in the most rapid currents, where all stagnation is pre- 
vented, and where the water is saturated with air, to which it has been 
exposed during its deposition from the clouds. It is the instinct leading 
these fish to seek a supply of air for their eggs which carries them from 
seas or lakes into the mountain country, which induces them to move 
against the stream, and to endeavour to overleap weirs, mill-dams, and 
eataracts. 



352 AQRICULTUBAL CHEMISTRY. 

It is evident, that in all cases of tiUage the seeds 
should be sown so as to be fiillj exposed to the infla- 
ence of the air. And one cause of the unproductitreneas 
of cold dajey adhesiye^oils is, that the seed is coated 
with matter impermeable to air. 

In sandy soils the earth is always sufficiently pene- 
trable by the atmosphere ; but in clayey soils there can 
scarcely be too great a mechanical division of parts in 
the process of tillage. Any seed not fully supplied 
with lur, always produces a weak and diseased plant. 

The process of malting, which has been already 
referred to, is merely a process in which germination is 
artificially produced ; and in which the starch of the 
cotyledon is changed into sugar ; which sugar is after- 
wards, by fermentation, converted into spirit 

It is very evident fi:om the chemical principles of 
germination, that the process of malting should be 
I carried on no fiuther than to produce the sprouting 
of the radicle, and should be checked as soon as this 
has made its distinct appearance. If it is pushed to 
such a degree as to occasion the perfect development of 
the radicle and the plume, a considerable quantity of 
saccharine matter will have been consumed in produc- 
ing their expansion, and there will be less spirit formed 
in fermentation, or produced in distillation. 

As this circumstance is of some importance, I made 
in October, 1806, an experiment relating to it I as- 
certained by the action of alcohol, the relative propor- 
tions of saccharine matter in two equal quantities of 
the same barley ; in one of which the germination had 
proceeded so far as to occasion a protrusion of the 
radicle to nearly a quarter of an inch beyond the grain 
in most of the specimens, and in the other of which it 
had been checked before the radicle was a line in 



LBCTURB V. 353 

length ; the quantity of sugar afforded by the last was 
to that in the first nearly as six to five. 

The saccharine matter in the cotyledons at the time 
of their change into seed-leaves^ renders them exceed- 
ingly liable to the attacks of insects : this principle is 
at once a nourishment of plants and animals, and the 
greatest ravages are committed upon crops in this first 
stage of their growth. 

The turnip fiy, an insect of the coleoptera genus, 
fixes itself upon the seed-leaves of the turnip at the 
time that they are beginning to perform their fimctions ; 
and when the rough leaves of the plume are thrown 
forth, it is incapable of injuring the plant to any extent 

Several methods have been proposed for destroying 
the turnip fly, or for preventing it firom injuring the 
crop. It has been proposed to sow radish-seed widi the 
turnip-seed, on the idea that the insect is fonder of the 
seed-leaves of the radish than those of the turnip : it is 
said that this plan has not been successfiil, and that the 
fly feeds indiscriminately on both. 

There are several chemical menstrua which render 
the process of germination much more rapid, when the 
seeds have been steeped in them. As in these cases 
the. seed-leaves are quickly produced, and more speedily 
perform their fimctions, I proposed it as a subject of 
experiment to examine whether such menstrua might 
not be usefiil in raising the turnip more speedily to that 
state in which it would be secure firom the fly ; but the 
result proved that the practice was inadmissible; for 
seeds so treated, though they germinated much quicker 
did not produce healthy plants, and often died soon 
after sprouting. 

I steeped radish-seeds in September, 1807, for twelve 
hours in a solution of chlorine, and similar seeds in 



354 AGRICULTURAL CHEMISTRY. 

very dilated nitric acid, in very dikited sulpjauoiic 
acid, in weak solution of ox jsulphate of iion, and 
some in common wat^. The seeds in solutions of 
chlorine and ox jsnlphate of iron tbxew out the germ 
in two days, those in nitric acid in three days, ia 
sulphuric acid in five, and those in water in seven 
days. But in the cases of premature germination 
though the plume was very vigorous for a short time, 
yet it became at the end of a fortnigbt weak and sickly; 
and at that period less vigorous in its growth than the 
sprouts which had be^i naturally devel(^;)edf so that 
there can be scarcely any useful appUcation of these 
experiments. Too rapid growth and prematuie decay 
seem invariably connected in organized structures^ Mid 
it is only by fdUowing the slow operations of natural 
causes, that we are capable of making improvements^ 

There is a number of chemical substances which are 
very offensive and even deadly to insects, which do not 
injure, and some of which even assist v^etatioii. 
Several of these mixtures have been tried with various 
success; a mixture of sulphur and lime, which is veiy 
destructive to slugs, does not prevent the ravages of the 
fly on the young turnip crop. His Grace the Duke of 
Bedford, at my suggestion, was so good as to order the 
experiment to be tried on a considerable scale at 
Wobum £surm ; the mixture of lime and sulphur was 
strewed over one part of a field sown with tumips; 
nothing was applied to the other part, but both were 
attacked nearly in the same manner by the fly. 

Mixtures of soot and quicklime, and urine and quick- 
lime, will probably be more eflScacious. The volatile 
alkali given off by these mixtures is offensive to insects; 
and they a^rd nourishment to the plant. Mr. T. A. 
Ejiight informs me, that he has tried the method b^ 



LBCTUBE y. 355 

ammoniooal fumes with success; but more extensire 
iriab are necessary to estoblish its general efficacy.* It 
may^ however, be safely adopted; for if it should fail iu 
destroying the fly, it will at least be a usefiil manure to 
the land. 

After the roots and leaves of the infimt plant are 
formed, the cells and tubes throughout its structure 
become filled with fluid, which is usually supplied from 

^ Mr. Knig^ has been so good as to ftur&ish me with the foUowlBg 
note on this subject. 

^ The experiment which I tried the year before last, and last year, to 
preserve turnips from the fly, has not been sufficiently often repeated to 
enable me to speak with any degree of decision ; and last year all my 
tamipe suooeeded perfoetly weR. In oonseqaence of your suggestion, 
when I had the pleasure to meet you some years ago at Holkham, that 
lime slaked with urine might possibly be found to kill, or drive oft, the 
Insects from a turnip crop, I tried that preparation in mixture with three 
parts of soot, which was put into a small barrd, with glmblet holes round 
it, to permit a certain quantity of the eompositkm, about four bushels to 
an acre, to pasa out and to fall into the drills with tbe turnip seeds. 
Whether it was by affording highly stimulating food to the plant, or 
giving some flavour which the flies did not like, I cannot tell ; but in the 
year 1811, the ad)olning rows were eaten away, and those to which the 
composition was applied, as above described, were scarcely at all touched. 
It is my intention in future to drill my crop in, first with the compo- 
sition on the top of the ridge; and then to sow at least a pound of seed, 
broad-cast, over the whole g^und. The ezi>ense of this will be very 
trifling, not more than 2t. per acre ; and the hone-hoe wlU instantly 
sweep away all supernumeraries between the rows, should those escape 
the flies, to which, however, they will be chiefly attracted ; because it 
it will always be found that those insects prefer turnips growing in poor 
to those in rich (pround. One advantage seems to be the acceleration 
given to the growth of the plants, by the highly stbnolative eifocts of the 
food they instantly receive, as soon as their growth commences, and long 
before their radicles have reached the dung. The directions above given 
apply only to turnips sowed upon ridges, with the manure immediately 
under them : and I am quite certain, that in all soils turnips should be 
thus cultivated. The dose vicinity of the manure, and the consequent 
short time required to carry the food into the leaf, and return the orga- 
nizable matter to the roots, are, in my hypothesis, points of vast impor* 
tance ; and the results hi practice are correspondent." 



356 AGRICULTURAL CHEMI8TRT. 

the soil, and the function of noorishment is performed 
by the action of its organ upon the external elements. 
The constituent parts of the air are subservient to this 
process ; but, as it might be expected, they act differ- 
endy under different circumstances. 

When a growing plant, the roots of which are sup- 
plied with proper nourishment, is exposed in the pre- 
sence of solar light to a given quantity of atmospherical 
air, containing its due proportion of carbonic acid, the 
carbonic acid after a certain time is destroyed, and a 
certain quantity of oxygen is found in its place. If 
new quantities of carbonic acid gas be supplied, the 
same result occurs ; so that carbon is added to plants 
from the air by the process of v^etation in sunshine ; 
and oxygen is added to the atmosphere. 

This circumstance is proved by a number of experi- 
ments made by Drs. Priestiey, Ingenhousz, and Wood- 
house, and M. T. de Saussure ; many of which I have 
repeated with similar results. The absorption of car- 
bonic acid gas and the production of oxygen are per- 
formed by the leaf; and leaves recentiy separated from 
the tree effect the change, when confined in portions of 
air containing carbonic acid; and absorb carbonic acid 
and produce oxygen even when immersed in water 
holding carbonic acid in solution. 

The carbonic acid is probably absorbed by the fluids 
in the cells of the green or parenchymatous part of the 
leaf; and it is from this part that oxygen gas is pro- 
duced during the presence of light M. Sennebier 
found that the leaf, from which the epidermis was 
stripped off, continued to produce oxygen when placed 
in water containing carbonic acid gas, and the globules 
of air rose from the denuded parenchyma ; and it is 
shown both from the experiments of Sennebier and 



LBCTURB V. 357 

Woodhouse^ that the leaves most abundant in parenchy- 
matous parts produce most oxygen in water impregnated 
with carbonic acid* 

Some few plants*' will vegetate in an artificial atmo- 
sphere, consisting principally of carbonic acid, and many 
will grow for some time in air containing from one-half 
to one-third ; but they are not so healthy as when sup- 
plied with smaller quantities of this elastic substance. 

Plants exposed to light have been found to produce 
oxygen gas in an elastic medium, and in water contain- 
ing no carbonic acid gas; but in quantities much 
smaller than when carbonic acid gas was present 

In the dark, no oxygen gas is produced by plants, 
whatever be the elastic medium to which they are ex- 
posed ; and no carbonic acid absorbed. In most cases, 
on the contrary, oxygen gas, if it be present, is absorbed, 
and carbonic acid gas is produced. 

In the changes that take place in the composition of 
the organized parts it is probable that saccharine com- 
pounds are principally formed during the absence of 
light; gum, woody fibre, oils, and resins, during its 
presence ; and the evolution of carbonic acid gas, or its 
formation during the night, may be necessary to give 
greater solubility to certain compounds in the plant I 
once suspected that all the carbonic acid gas, produced 
by plants in the night, or in shade, might be owing to 
the decay of some part of the leaf, or epidermis ; but 
the recent experiments of Mr. D. Ellis are opposed to 
this idea ; and I found that a perfectly healthy plant of 
celery, placed in a given portion of air for a few hours 
only, occasioned a production of carbonic acid gas^ and 
an absorption of oxygen. 

* I found the Arenaria tenuifolia to produce oxygen in carl>onic acid, 
which was nearly pure. 



358 AGRICULTiniAL CRBMI8TRY. 

Some persons have supposed that plants exposed in 
the free atmosphere to the vicissitodes of sanshine and 
shade, light and darkness, consume more oxygen than 
they produce, and that their permanent agency upon 
air is similar to that of animals ; and this opimion is 
espoused by the writer on the sobjeot just quoted, in 
his ingenious researches on vegetation. But idl experi- 
ments brought forwards in favour of this idea, and par- 
ticularly his experiments, have been made under cir- 
cumstances unfavourable to accuracy of result Tbe 
plants have been confined and supplied with food in an 
unnatural manner; and the influence of light upon 
them has been vei^ much diminished by the natoze of 
the media through which it passed. Plants confined 
in limited portions of atmospheric air soon become 
diseased; their leaves decay, and by their decomposition 
they rapidly destroy the oxygen of the air. In some 
of the early experiments of Dr. Priestley, before he 
was acquainted with the agency of light upon leaves, 
air that had supported combustion and Tespiration, was 
found purified by the growth of plants when they weie 
exposed in it for successive days and nights ; and his 
experiments are the more unexceptionable, as the plants^ 
in many of them, grew in their natural states; and 
shoots, or branches from them, only were introduced 
through water into the confined atmosphere. 

I have made some few researches on this subject, and 
I shall describe their results. On the 12th of July, 
1800, I placed a turf four inches square, clothed with 
grass, principally meadow fox-tail, and white clover, in 
a porcelain dish, standing in a shallow tray filled wiih 
water ; I then covered it with .a jar of flint glass, con- 
taining 380 cubical inches of common air in its natural 
state. It was exposed in a garden, so as to be liaUe to 



LECTURE V. 359 

the same changes with respect to light as in the common 
air. On the 20th of July the results were examined. 
There was an increase of the volume of the gas, 
amounting to fifteen cubical inches ; but the tempera- 
ture had changed from 64^ to 71^ ; and the pressure of 
the atmosphere, which on the 12th had been equal to 
the support of 30-1 inches of mercury, was now equal 
to that of 30*2. Some of the leaves of the white 
clover, and of the fox-tail were yellow, and the whole 
appearance of the grass less hedthy than when it was 
first introduced. A cubical inch of the gas, agitated in 
lime-water, gave a slight turbidness to the water; and 
the absorption was not quite -j^^ of its volume : 100 
parts of the residual gas exposed to a solution of green 
sulphate of iron, impregnated with nitrous gas, a sub- 
stance which rapidly absorbs oxygen from air, occa- 
sioned a diminution to 80 parts ; 100 parts of the air 
of the garden occasioned a diminution to 79 parts. 

If the results of this experiment be calculated upon, 
it will appear that the air had been slightly deteriorated 
by the action of the grasses. But the weather was un- 
usually cloudy during the progress of the experiment ; 
the plants had not been supplied in a natural manner 
with carbonic acid gas; and the quantity formed during 
the night, and, by the action of the faded leaves, must 
have been partly dissolved by the water ; and that this 
was actually the case, I proved by pouring lime-water 
into the water, when an immediate precipitation was 
occasioned. This increase of azote I am inclined to 
attribute to common air disengaged firom the water. 

The following experiment I consider as conducted 
under circumstances more analagous to those existing 
in nature. A turf four inches square, firom an irrigated 
meadow, clothed with common meadow grass, meadow 



360 AGRICULTURAL CHEMISTRY. 

fox-tail grass, and vernal meadow grass, was placed in a 
porcelain dish, which swam on the surface of water im- 
pregnated with carbonic acid gas. A vessel of thin flint 
glass, of the capacity of 230 cubical inches, having a 
funnel furnished with a stop-cock inserted in the top, 
was made to cover the grass ; and the apparatus was ex- 
posed in an open place ; a small quantity of water was 
daily supplied to the grass by means of the stop-oocL* 
Every day, likewise, a certain quantity of water was re- 
moved by a siphon, and water saturated with carbonic 
acid gas was supplied in its place ; so that it may be 
presumed that a small quantity of carbonic acid gas was 
constantly present in the receiver. On the 7th of July, 
1807, the first day of the experiment, the weather was 
cloudy in the morning, but fine in the afternoon ; the 
thermometer at 67, the barometer 30*2: towards the 
evening of this day a slight increase of the gas was per- 
ceived : the next three days were bright ; but in the 
morning of the 11th the sky was clouded; a consider- 
able increase of the volume of the gas was now observed: 
the 12th was cloudy, with gleams of sunshine; there 
was still an increase, but less than in the bright days : 
the 13th was bright About nine o'clock a.k. on the 
14th, the receiver was quite fiill ; and considering the 
original quantity in the jar, it must have been increased 
by at least 30 cubical inches of elastic fluid : at times, 
during this day, globules of gas escaped. At ten on the 
morning of the 15th, I examined a portion of the gas: 
it contained less than ^ of carbonic acid gas : 100 parts 
of it exposed to the impregnated solution left only 75 
parts ; so that the air was four per cent purer than the 
air of the atmosphere. 

I shall detail another similar experiment, made with 
♦ See Hg. 17. 



PLATE 10 



r 3t5.: 



Flu ^7 



-'A 



^ 






~- +----, 







LECTURE V. 361 

equally decisive results. A shoot from a vine, having 
three healthy leaves belonging to it, attached to its pa- 
rent tree, was bent so as to be placed under the receiver 
which had been used in the last experiment ; the water 
confining the common air was kept in the same manner 
impregnated with carbonic acid gas: the experiment 
was carried on from August 6th, till August 14th, 1807: 
during this time, though the weather had been generally 
clouded, and there had been some rain, the volume of 
elastic fluid continued to increase. Its quality was ex- 
amined on the morning of the 15th ; it contained -^^ of 
carbonic acid gas, and 100 parts of it afforded 23*5 of 
oxygen gas. 

These facts confirm the popular opinion, that when 
the leaves of vegetables perform their healthy functions, 
they tend to purify the atmosphere in the common 
variations of weather, and changes from light to darkness. 
In germination, and at the time of the decay of the 
leaf, oxygen must be absorbed ; but when it is considered 
how large a part of the surface of the earth is clothed 
with perennial grasses, and that half of the globe is al- 
ways exposed to the solar light, it appears by far the 
most probable opinion, that more oxygen is produced 
than consumed during the process of vegetation : and 
that it is this circumstance which is the principal cause 
of the uniformity of the constitution of the atmosphere. 
Animals produce no oxygen gas during the exercise 
of any of their fimctions, and they are constantly con- 
suming it; but the extent of the animal, compared to 
that of the vegetable kingdom, is very small ; and the 
quantity of carbonic acid gas produced in respiration, 
and in various processes of combustion and fermenta- 
tion, bears a proportion extremely minute to the whole 
volume of the atmosphere : if every plant, during the 

VOL. VIL R 



AGRICULTURAL CHEMISTRY. 

progress of its life, makes a very small addition of oxy- 
gen to the air, and occasions a very small consumption 
of carbonic acid, the effect may be conceived adequate 
to the wants of nature. 

It may occur as an objection to these views, that if 
the leaves of plants purify the atmosphere, towards the 
end of autumn, and through the winter, and early spring, 
the air in our climates must become impure, the oxygen 
in it diminish, and the carbonic acid gas increase, which 
is not the case ; but there is a very satis&ctory answer 
to this objection. The different parts of the atmo^here 
are constantly mixed together by winds, which, when 
they are strong, move at the rate of from 60 to 100 
miles in an hour. In our winter, the south-west gales 
convey air which has been purified by the vast forests 
and savannahs of South America, and which, passing 
over the ocean, arrives in an uncontaminated state. The 
storms and tempests which often occur at the begin- 
ning, and towards the middle of our winter, and which 
generally blow from the same quarter of the globe, have 
a salutary influence. By constant agitation and mo- 
tion, the equilibrium of the constituent parts of the at- 
mosphere is preserved ; it is fitted for the purposes of 
life ; and those events which the superstitious formerly 
referred to the wrath of Heaven, or the agency of evU 
spirits, and in which they saw only disorder and con- 
fusion, are demonstrated, by science, to be ministrations 
of Divine intelligence, and connected with the order and 
harmony of our system. 

I have reasoned, in a former part of this Lecture, 
against the close analogy which some persons have as- 
sumed between the absorption of oxygen and the forma- 
tion of carbonic acid gas in germination, and in the res- 
piration of the foetus. Similar arguments will apply 



LECTURE y. 363 

against the pursuits of this analogy^ betsireen the ftmc- 
tions of the leaves of the adult plant, and those of the 
lungs of ihe adult animal. Plants grow vigorously only 
when supplied with light ; and most species die if de- 
prived of it It cannot be supposed that the production 
of oxygen from the leaf, which is known to be con- 
nected with its natural colour, is the exertion of a dis- 
eased function, or that it can acquire carbon in the 
day-time, when it is in most vigorous growth, when the 
sap IS rising, when all its powers of obtaining nourish- 
ment are exerted, merely for the purpose of giving it off 
again in the night, when its leaves are closed, when the 
motion of the sap is imperfect, and when it is in a state 
approaching to that of quiescence. Many plants that 
grow upon rocks, or soils, containing no carbonic mat- 
ter, can only be supposed to acquire their charcoal from 
the carbonic acid gas in the atmosphere ; and the leaf 
may be considered at the same time as an organ of ab- 
sorption, and an organ in which the sap may undeigo 
difierent chemical changes. 

When pure water only is absorbed by the roots oi 
plants, the fluid, in passing into the leaves, will probably 
have greater power to absorb carbonic acid from the at- 
mosphere. When the water is saturated with carbonic 
acid gas, some of this substance, even in the sunshine, 
may be given off by the leaves ; but a part of it likewise 
will be always decomposed, which has been proved by 
the experiments of M. Sennebier. 

When the fluid taken up by the roots of plants 
contains much carbonaceous matter, it is probable 
that plants may give off carbonic acid from their 
leaves even in the sunshine. In shorty the frinotion 
of the leaf must vary according to the composition 
of the sap passing through it, and according to the 

r2 



364 AGRICULTURAL CHEMISTRY. 

nature of th^ products which are formed from it. 
When sugar is to be produced^ as in early spring 
at the time of the development of buds and flowers, 
it is probable that less oxygen will be given off than 
at the time of the ripening of the seed, when starch, 
or gums^ or oils, are formed; and the process of 
ripening the seed usually takes place when the agency 
of the solar light is most intense. When the acid 
juices of fruits become saccharine in the natural 
process of vegetation, more oxygen, there is every 
reason to believe, must be given off, or newly combined, 
than at other times ; for, as it was shown in the Third 
Lecture, all the vegetable acids contain more oxygen 
than sugar. It appears probable, that in some cases 
in which oily and resinous bodies are formed in vegeta- 
tion, water may be decomposed ; its oxygen set free, and 
its hydrc^en absorbed. 

M. Berard, of Montpellier, has shown that fruits 
in ripening convert the oxygen of the air into carbonic 
acid ; and that the process of ripening may be sus- 
pended by the exclusion of the fruit from oxygen gas, 
and that it will go on again Sitter a certain interval 
of time. Unripe peaches, plums, and apricots, may be 
preserved in close bottles, filled with air deprived of 
oxygen, for from twenty days to a month ; and pears 
and apples about three months, when they will after- 
wards ripen perfectly by exposure to air. 

I have already mentioned, that some plants produce 
oxygen in pure water. Dr. Ingenhousz found this to 
be the case with species of the confervas. I have tried 
the leaves of many plants, particularly those that pro- 
duce volatile oils. When such leaves are exposed 
in water saturated with oxygen gas, oxygen is given off 
in the solar light; but the quantity is very small. 



LECTURE V. 365 

and always limited ; nor have I been able to ascertain 
with certainty whether the vegetable powers of the 
leaf were concerned in the operation, though it seems 
probable. I obtained a considerable quantity of oxygen 
in an experiment made fifteen years ago, in which 
vine leaves were exposed to pure water; but on repeat- 
ing the trial often since, the quantities have always been 
very much smaller. I am ignorant whether this 
difference is owing to the peculi^ state of the leaves, 
or to some confervse which might have adhered to the 
vessel, or to other sources of fallacy. 

The most important and most common products of 
vegetables, mucilage, starch, sugar, and woody fibre, are 
composed of water, or the elements of water in their 
due proportion, and charcoal; and these, or some of them, 
exist in all plants : and the decomposition of carbonic 
acid, and the combination of water in vegetable struc- 
tures, are processes which must occur almost universally. 

When glutinous and albuminous substances exist 
in plants, the azote they contain may be suspected 
to be derived from the atmosphere; but no experi- 
ments have been made which prove this ; they might 
easily be instituted upon mushrooms and fiinguses. 

In cases in which buds are formed, or shoots thrown 
forth firom roots, oxygen appears to be uniformly 
absorbed, as in the germination of seeds. I exposed a 
small potato, moistened with common water, to 24 
cubical inches of atmospherical air, at a temperature of 
59°. It began to throw forth- a shoot on the third day ; 
when it was half an inch long I examined the air.; 
nearly a cubical inch of oxygen was absorbed, and 
about three-fourths of a cubical inch of carbonic acid 
formed. The juices in a shoot separated firom the 
potato had a sweet taste ; and the absorption of oxygen. 



366 AGRICULTURAL CHEMISTRY. 

and the production of catbonic acid^ were probablj 
connected with the conversLon of a portion of starch 
into sugar. When potatoes that have been firos^i are 
thawed, they become sweet; probably oxygen is 
absorbed in this process; if so, the change may be 
prevented by thawing them out of the contact of 
air ; under water, for instance, that has been recentiy 
boiled 

In the tiUering of com, tiiat is, the production of new 
stalks round the original plume, there is every reason to 
believe tiiat oxygen must be absorbed ; for die stalk at 
which the tillering takes place always contains sugar, 
and the shoots arise fix>m a part deprived of light 
The drill husbandry favours this process; for loose 
earth is thrown by hoeing round the stalks: they 
are preserved from light, and yet supplied with oxyg^en. 
I have counted from 40 to 120 stalks produced from a 
grain of wheat, in a moderately g^ood crop of drilled 
wheat And we are informed by Sir Eenelm Digby, 
in 1660, that there was in the possession of the Fathers 
of the Christian Doctrine at Paris, a plant of barley, 
which they, at that time, kept by them as a curiosity, 
and which consisted of 249 stalks springing from one 
root, or grain ; and in which they counted above 18,000 
grains or seeds of barley. 

The great increase which takes place in fthe trans- 
plantation of wheat depends upon the circumstance, 
that each layer thrown out in tillering may be removed, 
and treated as a distinct plant In the Philosophical 
Transactions, vol. Iviii. p. 203., the following statement 
may be found: Mn C. Miller, of Cambridge, sowed 
some wheat on the 2d of June, 1766; and on the 8th 
of August, a plant was taken and separated into 18 
parts, and replanted ; these plants were again taken up. 



LECTURE V. 367 

and divided in the months of September and October, 
and planted separately to stand the winter, which 
division produced 67 plants. They were again taken 
up in March and April, and produced 500 plants : the 
number of ears thus formed from one grain of wheat 
was 21,109, which gave three pecks and three quarters 
of com that weighed 47lb8. 7oz., and that were 
estimated at 576,840 grains. 

It is evident from the statements just given, that 
the change which takes place in the juices of the leaf 
by the action of the solar light, must tend to increase 
the proportion of inflammable matter to their other 
constituent parts. And the leaves of the plants that 
grow in darkness or in shady places are uniformly pale; 
their juices are watery and saccharine, and they do not 
afford oils or resinous substances. I shall detail an 
experiment on this subject. 

I took an equal weight, 400 grains, of the leaves of 
two plants of endive; one bright green, which had 
grown fully exposed to light, and the other almost 
white, which had been secluded from light by being 
covered with a box ; after being both acted upon for 
some time by boiling water, in the state of pulp, the 
undissolved matter was dried, and exposed to the action 
of warm alcohol. The matter from the green leaves 
gave it a tinge of olive ; that from the pale leaves did 
not alter its colour. Scarcely any solid matter was pro- 
duced by evaporation of the dcohol that had been 
digested on the pale leaves : whereas by the evapora- 
tion of that from the green leaves a considerable 
residuum was obtained; five grains of which were 
separated from the vessel in which the evaporation was 
carried on ; they burnt with flame, and appeared partly 
matter analogous to resin: 53 grains of woody fibre 



368 AGRICULTURAL CHEMISTRY. 

were obtained from the green leaves^ and onij 31 from 
the pale leaves. 

It has been mentioned in the Third Lecture^ that 
the sap probably^ in common cases, descends fix>m the 
leaves into the bark ; the bark is usually so loose in its 
texture, that the atmosphere may possibly act upon it in 
the cortical layers ; but the changes taking place in the 
leaves appear sufficient to explain the difference between 
the products obtained from the bark and from the 
alburnum; the first of which contains more car- 
bonaceous matter than the last. 

When the similarity of the elements of different 
vegetable products is considered according to the views 
given in the Third Lecture, it is easy to conceive how 
the different organized parts may be formed from the 
same sap, according to the manner in which it is acted 
on by heat, light, and air. By the abstraction of 
oxygen, the different inflammable products, fixed and 
volatile oils, resins, camphor, woody fibre, &c. may be 
produced from saccharine or mucilaginous fluids ; and 
by the abstraction of carbon and hydrogen, starch, 
sugar, the different vegetable acids and substances 
soluble in water, may be formed with highly combustible 
and insoluble substances. Even the limpid volatile oils 
which convey the fragrance of the flower, consist of 
different proportions of the same essential elements 
as the dense woody fibre ; and both are formed by 
different changes in the same oi^ans, from the same 
materials, and at the same time. 

M. Vauquelin has lately attempted to estimate the 
chemical changes taking place in vegetation, by ana- 
lyzing some of the organized parts of the horse-chesnut 
in their different stages of growth. He found in the 
buds collected, March 7, 1812, tanning principle, and 



LECTURE V. 369 

albuminous matter capable of being obtained separately, 
but, when obtained, combining with each other. In 
the scales surrounding the buds, he found the tanning 
principle, a little saccharine matter, resin, and a fixed 
oil. In the leaves fully developed, he discovered the 
same principles as in the buds; and in addition, a 
peculiar green resinous matter. The petals of the 
flower yielded a yellowish resin, saccharine matter, 
albuminous matter, and a little wax : the stamina 
afforded sugar, resin, and tannin. 

The young chesnuts examined immediately after 
their formation, afforded a large quantity of a matter 
which appeared to be a combination of albuminous 
matter and tannin. All the parts of the plant afforded 
saline combinations of the acetic and phosphoric acids. 

M. Vauquelin could not obtain a sufiicient quantity 
of the sap of the horse-chesnut for examination, a cir- 
cumstance much to be regretted ; and he has not stated 
the relative quantities of the different substances in the 
buds, leaves, flowers, and seeds. It is probable, how- 
ever, firom his unfinished details, that the quantity of re- 
sinous matter is increased in the leaf, and that the white 
fibrous pulp of the chesnut is formed by the mutual 
action of albuminous and astringent matter, which pro- 
bably are supplied by different cells or vessels. I have 
already mentioned ^ that the cambium, from which the 
new parts in the trunk and branches appear to be formed, 
probably owes its power of consolidation to the mixture 
of two different kinds of sap ; one of which flows up- 
wards firom the roots, and the other of which probably 
descends fi-om the leaves. I attempted, in May, 1804, 
at the time the cambium was forming in the oak, to as- 
certain the nature of the action of the sap of the albur- 
* Pag:e296. 
r5 



370 AGRICULTURAL CHEMISTRY. 

num upon the juices of the bark. By perforating the 
alburnum in a young oak, and applying an exhausting 
syringe to the aperture, I easily drew out a small quan* 
tity of sap. I could not, however, in the same way ob- 
tain sap from the bark. I was obliged to recur to the 
solution of its principles in water, by infiising a small 
quantity of fresh bark in warm water ; the liquid ob- 
tained in this way, was highly coloured and astringent; 
and produced an immediate precipitate in the albumous 
sap, the taste of which was sweetish, and slightly astrin- 
gent, and which was colourless. 

The increase of trees and plants, must depend upon 
the quantity of sap which passes into their oigans ; upon 
the quality of this sap ; and on its modification, by the 
principles of the atmosphere. Water, as it is the ve- 
hicle of the nourishment of the plant, is the substance 
principally given off by the leaves. Dr. Hales found 
that a sunflower, in one day of twelve hours, transpired 
by its leaves one pound fourteen ounces of water, all 
of which must have been imbibed by its roots. 

The powers which cause the ascent of the sap, have 
been slightly touched upon in the Second and Third 
Lectures. The roots imbibe fluids from the soil, by 
capillary attraction ; but this power alone is insufficient 
to account for the rapid elevation of the sap into the 
leaves. This is fully proved by the following fact, de- 
tailed by Dr. Hales, vol. i. of the Vegetable Staticst, 
page 114. : — A vine branch of four or five years old was 
cut through, and a glass tube carefully attached to it ; 
this tube was bent as a siphon, and filled with quick- 
silver ; so that the force of the ascending sap could be 
measured by its effect in elevating the quicksilver. In 
a few days it was found that the sap had been propelled 
forwards with so much force, as to raise the quicksilver 



LECTURE V. 371 

to 38 inches, which is a force considerably superior to 
that of the usual pressure of the atmosphere. Capillary 
attraction can only be exerted by the sur&ces of small 
vessels, and can never raise a fluid into tubes above the 
vessels themselves. 

I refeired in the beginning of the Third Lecture, to 
Mr. Knight's opinion, that the contractions and expan- 
sions of the silver grain in the alburnum, are the most 
efficient cause of the ascent of the fluids contained in its 
pores and vessels. The views of this excellent physio* 
legist, are rendered extremely probable, by the facts he 
has brought forward in support of them. Mr. Knight 
found that a very small increase of temperature was suf- 
ficient to cause the fibres of the silver grain to separate 
firom each other, and that a very slight diminution of 
heat produced their contraction. The sap rises most 
vigorously in spring and autumn, at the time the tem- 
perature is variable ; and if it be supposed that, in ex- 
panding and contracting, the elastic fibres of the silver 
grain exercise a pressure upon the cells and tubes con- 
taining the fluid absorbed by the capillary attraction of 
the roots, this fluid must constantly move upwards 
towards the points where a supply is; needed 

The experiments of Montgolfier, the celebrated in- 
ventor of the balloon, have shown that water may be 
raised almost to an indefinite height by a very small 
force, provided its pressure be taken off by continued 
divisions in the column of fluid. This principle, there 
is great reason to suppose, must operate in assisting the 
ascent of the sap in the cells and vessels of plants which 
have no rectilineal communication, and which every- 
where oppose obstacles to the perpendicular pressure of 
the sap. 

The changes taking place in the leaves and buds, and 



372 AGRICULTUBAL CHEMISTRY. 

the degree of their power of transpiration, must be inti* 
mately connected likewise with the motion of the sap 
upwards. This is shown by several experiments of Dr. 
Hales. 

A branch from an apple -tree was separated and intro- 
duced into water» and connected with a mercurial gauge. 
When the leaves were upon it, it raised the mercury, by 
the force of the ascending juices, to four inches ; but a 
similar branch, from which the leaves were removed, 
scarcely raised it a quarter of an inch. 

Those trees, likewise, whose leaves are soft, and of a 
spongy texture, and porous at their upper sur&oes, dis- 
played by far the greatest powers with regard to the 
elevation of the sap. 

The same accurate philosopher, whom I have just 
quoted, found that the pear, quince, cherry, walnut, 
peach, gooseberry, water-elder, and sycamore, which 
have all soft and unvarnished leaves, raised the mercury 
under favourable circumstances from three to six inches. 
Whereas the elm, oak, chesnut, hazel, sallow, and ash, 
which have firmer and more glossy leaves, raised the 
mercury only from one to two inches. And the ever- 
greens, and trees bearing varnished leaves, scarcely at 
all affected it; particularly the laurel and the laurus- 
tinus. 

It will be proper to mention the facts which show 
that, in many cases, fluids descend through the bark. 
Mr. Knight has shown, in the Philosophical Transac- 
tions, that long strips of bark, everywhere detached 
from the alburnum of the tree, except at their upper 
ends, deposited as much alburnum as they could have 
done, if they had retained their natural position. In 
these cases, the sap must have descended through the 
bark wholly. 



LECTUftE V. 373 

M. Baisse placed branches of different trees in an 
infusion of madder, and kept them there for a long 
time. He found, in all cases, that the wood became 
red before the bark; and that the bark began to receive 
no tinge till the whole of the wood was coloured, and 
till the leaves were affected; and that the colouring 
matter first appeared above, in the bark immediately in 
contact with the leaves. 

Similar experiments were made by M. Bonnet, and 
with analogous results, though not so perfectly distinct 
as those of M. Baisse. 

Du Hamel found that, in different species of the pine 
and other trees, when strips of bark were removed, the 
upper part of the wound only emitted fluid, whilst the 
lower part remained dry. 

This may likewise be observed in the summer in fruit 
trees, when the bark is wounded, the alburnum remain- 
ing untouched* 

The motion of the sap through the bark, seems prin- 
cipally to depend upon gravitation. When the watery 
particles have been considerably dissipated by the trans- 
piring functions of the leaves, and the mucilaginous, 
inflammable, and astringent constituents, increased by 
the agency of heat, light, and air, the continued impulse 
upwards from the alburnum, forces the remaining in- 
spissated fluid into the cortical vessels, which receive no 
other supply. In these, from its weight, its natural ten- 
dency must be to descend: and the rapidity of the 
descent, must depend upon the general consumption of 
the fluids of the bark in the living processes of vegeta- 
tion ; for there is every reason to believe that no fluid 
passes into the soil through the roots ; and it is impos- 
sible to conceive a free lateral communication between 
the absorbent vessels of the alburnum in the roots, and 



374 AGRICULTURAL CHEMISTRY. 

the transporting or carrying vessels of the bark ; for if 
such a communication existed, there is no reason vfhj 
the sap should not rise through the bark, as well as 
through the alburnum; for the same physical powers 
would then operate upon both. 

Some authors have supposed that the sap rises in the 
alburnum, and descends through the bark, in conse- 
quence of a power similar to that which produces the 
circulation of the blood in animals ; a force analogous to 
the muscular force in the sides of the vessels. 

This analogy has, however, in general, been too mfich 
insisted upon, and too loosely stated; there are un- 
doubtedly resemblances more or less remote in eveiy 
part of created nature ; but the irritability of the mus- 
cular fibre in animals, and the contractibility of the vas- 
cular system in plants, appear to depend upon entirely 
different causes. 

In crystallization, or the regular arrangement of in- 
organic substancesf, there is a constant increase of 
mattter from the attraction and juxtaposition of like 
parts or molecules. In vegetation a germ expands by 
the assimilation of a variety of new aliments, and by 
powers entirely different from those of common in- 
organic matter; but there seems to be no system of 
nerves, as in animals, which is essential to irritability. 
We know so little of the refined powers and properties 
of matter, that we can give little more than vague 
hypotheses as to the cause of the movement of the 
fluids in the vegetable cells or tubes; yet it is im- 
possible not to allow common material agents a much 
greater share in producing this phenomenon, than they 
exercise in animal life. 

Whoever will peruse any considerable part of the 
Vegetable Statics of Hales, must receive a deep im- 



LECTURE V. 376 

pression of the dependence of the motion of the sap 
upon physical causes. In the same tree, this sagacious 
person observed that in a cold cloudy morning, when 
no sap ascended, a sudden change was produced by a 
gleam of sunshine of half an hour, and a vigorous 
motion of the fluid. The alteration of the wind fix>m 
south to the north immediately checked the effect On 
the coming on of a cold afternoon after a hot day, the 
sap that had been rising began to fall. A warm shower 
and a sleet storm produced opposite effects. 

Many of his observations likewise show that the dif- 
ferent powers which act in the adult tree, produce dif- 
ferent effects at different seasons. 

Thus in the early spring, before the buds expand, the 
variations of the temperature, and changes of the state 
of the atmosphere with regard to moisture and dryness, 
exert their great effects upon the expansions and con- 
tractions of the vessels ; and then the tree is in what is 
called by gardeners its bleeding season. 

When the leaves are fully expanded, the great deter- 
mination of the sap is to these new oigans. And hence 
a tree which emits sap copiously from a wound whilst 
the buds are opening, will no longer emit it in summer 
when the leaves are perfect; but in the variable weather, 
towards the end of autumn, when the leaves are falling, 
it will again possess the power of bleeding in a very 
slight degree in the warmest days; but at no other 
times. 

In all these circumstances there is nothing truly 
analogous to the irritable action of animal systems. 

In animal systems the heart and arteries are in con- 
stant pulsation. Their functions are unceasingly per- 
formed in all climates, and in all seasons ; in winter, as 
well as in spring ; upon the arctic snows, and under the 



376 AGRICULTURAL CHEMISTRY. 

tropical suns. They neither cease in the periodical 
nocturnal sleep^ common to most animals ; nor in the 
long sleep of winter, peculiar to a few species. The 
power is connected with animation, is limited to beings 
possessing the means of voluntary locomotion ; it co- 
exists with the first appearance of vitality ; it disappears 
only with the last spark of life. 

As the operation of the different physical agents upon 
the sap vessels of plants ceases, and the fluid becomes 
quiescent, the materials dissolved in it by heat are de- 
posited in the cells of the alburnum ; and in conse- 
quence of this deposition, a nutritive matter is provided 
for the first wants of the plant in early spring, to assist 
the opening of the buds, and their expansion, when the 
motion from the want of leaves is as yet feeble. 

This beautiful principle in the vegetable economy 
was first pointed out by Dr. Darwin ; and Mr. Knight 
has given a number of experimental elucidations of it. 

Mr. Knight made numerous incisions into the al- 
burnum of the sycamore and the birch, at different 
heights; and in examining the sap that flowed from 
them, he found it more sweet and mucilaginous in pro- 
portion as the aperture from which it flowed was elevated ; 
which he could ascribe to no other cause than to its 
having dissolved sugar and mucilage, which had been 
stored up through the winter. 

He examined the alburnum in different poles of oak 
in the same forest; of which some had been felled in 
winter, and others in summer; and he always found 
most soluble'^matter in the wood felled in winter, and 
its specific gravity was likewise greater. 

In all perennial trees this circumstance takes place ; 
and likewise in grasses and shrubs. The joints of the 
perennial grasses contain more saccharine and mucila- 



LECTURE V. 377 

ginous matter in winter than at any other season ; and 
this is the reason why the fiorin or Agrostis alba, 
which abounds in these joints^ affords so useful a winter 
food. 

The roots of shrubs contain the lai^est quantity of 
nourishing matter in the depth of winter; and the bulb 
in all plants possessing it is the receptacle in which 
nourishment is hoarded up during winter. 

In annual plants the sap seems to be fiilly exhausted 
of all its nutritive matter by the production of flowers 
and seeds ; but if parts of annual plants, having leaves 
and buds, be detached and kept, so that they do not 
expend themselves by affording blossoms or seeds, the 
same individual life may be preserved through many 
years. It appears, therefore, as Mr. Knight observes, 
to be habit only, not life, that is annual in such plants. 

When perennial grasses are cropped very close by 
feeding cattle late in autumn, it has been often observed 
by farmers that they never rise vigorously in the spring; 
and this is owing to the removal of that part of the 
stalk which would have afforded them concrete sap, 
their first nourishment 

Ship builders prefer for their purposes that kind of 
oak-timber afforded by trees that have had their bark 
stripped off in spring, and which have been cut in the 
autumn or winter following. The reason of the supe- 
riority of this timber is, that the concrete sap is ex- 
pended in the spring in the sprouting of the leaf; and 
the circulation being destroyed, it is not formed anew ; 
and the wood having its pores free from saccharine 
matter, is less liable to undergo fermentation from the 
action of moisture and air. 

In perennial trees a new alburnum, and consequently 
a new system of vessels, is annually produced, and the 



378 AGRICULTTTRAL CHEMISTRY. 

nutriment for the next year deposited in them ; so that 
the new buds, like the plume of the seed, are supplied 
with a reservoir of matter essential to their first deve- 
lopment. 

The old alburnum gradually loses its vascalar stroe- 
ture, and, being constantly pressed upon by the expan- 
sive force of the new fibres, becomes harder, denser, 
and at length becomes heart-wood; and in a certain 
time obeys the common laws of dead matter, decays, 
decomposes, and is converted into aeiifonn and carbonic 
elements ; into those principles fix>m which it was ori- 
ginally formed. 

The decay of the heart-wood seems to constitute the 
great limit to the age and size of trees. And in young 
branches firom old trees, it is much more liable to de- 
compose than in similar branches from seedlings. This 
is likewise the case with grafts. The graft is only nou- 
rished by the sap of the tree to which it is transferred ; 
its properties are not changed by it: the leaves, bloe- 
soms, and fiuits are of the same kind as if it had vege- 
tated upon its parent stock. The only advantage to be 
gained in this way, is the affording to a graft firom an 
old tree a more plentiful and healthy food than it could 
have procured in its natural state ; it is rendered for a 
time more vigorous, and produces fitirer blossoms and 
richer fiiiits. But it partakes not merely of the obvious 
properties, but likewise of the infirmities and disposition 
to old age and decay, of the tree whence it sprung. 

This seems to be distinctly shown by the observations 
and experiments of Mr. Knight. He has, in a number 
of instances, transferred the young scions and healthy 
shoots firom old esteemed firuit-bearing trees to young 
seedlings. They flourished for two or three years ; but 
they soon became diseased and sickly, like their parent 
trees. 



LECTURE V. 379 

It is firom this cause that so many of the apples for- 
merly celebrated for their taste and their uses in the 
manufacture of cyder are gradually deteriorating, and 
many will soon disi^pear. The red streak, and the 
moil, so excellent in the beginning of the last century, 
are now in the extremest stage of their decay ; and 
however carefiilly they are ingrafted, they merely tend 
to multii^y a sickly and exhausted variety.''^ 

The trees possessing the firmest and the least porous 
heart-wood are the longest in duration. 

In general, the quantity of charcoal afforded by woods 
offers a tolerably accurate indication of their durability : 
those most abundant in charcoal and earthy matter are 
most permanent; and those that contain the largest 
proportion of gaseous elements are the most destruc- 
tible. 

Amongst our own trees, the chesnut and the oak are 
pre-eminent as to durability ; and the chesnut affords 
rather more carbonaceous matter than the oak. 

In old Gothic buildings these woods have been some- 
times mistaken one for the other; but they may be 
easily known by this circumstance, that the pores in the 
alburnum of the oak are much larger and more thickly 
set, apd are easily distinguished ; whilst the pores in 
the chesnut require glasses to be seen distinctly. 

In consequence of the slow decay of the heart^wood 
of the oak and chesnut, these trees, under &YOurable 
circumstances, attain an age which cannot be much 
short of 1000 years. 

The beech, the ash, and the sycamore, most likely 
-never live half as long. The duration of the apple-tree 
is not, probably, much more than 200 years ; but the 

* [The accuracy of this doctrine has been questioned ; yide M. de 
CandoUe's Physiologie V6g6tale, liy. 4. chap, zi.] 



380 AGRICULTUBAL CHBMI8TBY. 

pear-tree^ according to Mr. Knight, lives through double 
this period. Most of our best apples are supposed to 
have been introduced into Britain by a firuitcrcr of 
Henry the Eighth^ and they are now in a state of old 
age. 

The oak and chesnut decay much sooner in a moist 
situation than in a dry and sandy soil; and their timber 
is less firm. The sap vessels in such cases are more 
expanded^ though less nourishing matter is carried into 
them; and the general texture of the formations of 
wood necessarily less firm. Such wood splits more 
easily, and is more liable to be affected by variations in 
the state of the atmosphere. 

The same trees, in general, are much longer-lived in 
the northern than in the southern climates. The rea- 
son seems to be, that all fermentation and decomposi- 
tion are checked by cold ; and at very low temperatures 
both animal and vegetable matters altogether resist 
putrefaction : and in the northern winter, not only ve- 
getable Ufe, but likewise vegetable decay, must be at a 
stand 

The antiputrescent quality of cold climates is fully 
illustrated in the instances of the rhinoceros and mam- 
moth, lately found in Siberia, entire beneath the firozen 
soil, in which they must probably have existed from the 
time of the deluge. I examined a part of the skin of 
the mammoth sent to this country, on which there was 
some coarse hair ; it had all the chemical characters of 
recently dried skin. 

Trees that grow in situations much exposed to winds, 
have harder and firmer wood than such as are consider- 
ably sheltered. The dense sap is determined by the 
agitation of the smaller branches to the trunk and larger 
branches, where the new alburnum formed is conse- 



LECTURE V. 381 

quently thick and firm. Such trees abound in the 
crooked limbs fitted for forming knee-timber, which is 
necessary for joining the decks and the sides of ships. 
The gales in elevated situations gradually act so as to 
give the tree the form best calculated to resist their 
effects. And the mountain oak rises robust and sturdy ; 
fixed firmly in the soil, and able to oppose the full 
force of the tempest. 

The decay of the best varieties of finit-bearing trees 
which have been distributed through the country by 
grafts is a circumstance of great importance. There is 
no mode of preserving them ; and no resource, except 
that of raising new varieties by seeds. 

Where a species has been ameliorated by culture, the 
seeds it affords, other circumstances being similar, pro- 
duce more vigorous 'and perfect plants; and in this 
way the great improvements in the production of our 
fields and gardens seem to have been occasioned. 

Wheat, in its indigenous state, as a natural produc- 
tion of the soil, appears to have been a very smaU grass ; 
and the case is still more remarkable with the apple 
and the plum. The crab seems to have been the parent 
of all our apples. And two firuits can scarcely be con- 
ceived more different, in colour, size, and appearance, 
than the wild plum and the rich magnum bonum. 

The seeds of plants exalted by cultivation always fur- 
nish lai^ and improved varieties ; but the flavour, and 
even the colour of the fruit, seems to be a matter of 
accident Thus a hundred seeds of the golden pippin 
will all produce fine large-leaved apple-trees, bearing 
firuit of a considerable size ; but the tastes and colours 
of the apples firom each will be different, and none will 
be the same in kind as those of the pippin itself. Some 
will be sweet, some sour, some bitter, some mawkish. 



382 AGRICULTURAL ^CHEMISTRY. 

some aromatic; some yellow^ some green, some red, 
and some streaked. All the apples wiU, however, be 
much more perfect than those from the seeds of a craby 
which produce trees all of the same kind, and all bear- 
ing sour and dinimitiTe firoit. 

The power of the horticulturist extends only to the 
multiplying excellent Tarieties by grafting. They can- 
not be rendered permanent; and the good fruits at pre- 
sent in our gardens are the produce of a few seedlings, 
selected probably from hundreds of thousands; the re- 
sults of great labour and industry, and midtiplied ex- 
pernnents. 

The laiger and diicker the leaives of a seedling, and 
the more expanded its blossoms, the more it is likely to 
produce a good variety of fruit. Short4eaved trees 
should never be selected ; for these apjffoach nearer to 
the original standard : whereas the other qualities indi- 
cate the influence of cultivadon. 

In the general selection of seeds, it would appear that 
those arising from the most highly cultivated varieties 
of plants are such as give the most vigorous produce ; 
but it is necessary from time to time to change, and, as 
it were, to cross the breed. 

By applying the poUen, or dust of tlie stamina, tnm 
one variety to the pistil of another of the same species, 
a new varie^ may be easily produced ; and Mr. Knight's 
experiments seem to warrant the idea that great advan- 
tages may be derived from this method of propagation. 

Mr. E^ight's large peas, produced by crossing two 
varieties, are celebrated amongst horticulturists, and 
wiU, I hope, soon* be cultivated by fiinneni. 

I have seen several of his crossed apples, which 
promise to rival the best of those which are gradually 
dying away in the cider countries. 



LECTURE V. 383 

And his experiments on the crossing of wheat, which 
is very easily effected, merely by sowing the different 
kinds together, lead to a result which is of considerable 
importance. He says, in the Philosophical Transac- 
tions for 1799, '<In the years 1795 and 1796, when 
almost the whole crop of com in the island was blighted, 
the varieties obtained by crossing ahne escaped, though 
sown in several soils, and in very different situa- 
tions," 

The processes of gardening for increasing the num- 
ber of fruit-bearing branches, and for improving the 
fruit upon particular branches, will all admit of eluci- 
dation from the principles that have been advanced in 
this lecture. 

By making trees espaliers, the force of gravity is 
particularly directed towards the lateral parts of the 
branches and more sap determined towards the fruit 
buds ; and hence they are more likely to bear when in 
a horizontal than when in a vertical position. 

The twisting of a wire, or tying a thread round a 
branch, has been often recommended as a means of 
making it produce fruit In this case the descent of 
the sap in the bark must be impeded above the ligature ; 
and more nutritive matter consequently retained and 
^plied to the expanding parts. 

In engrafting, the vessels of the bark of the stock 
and the graft cannot so perfectly come in contact as the 
albumous vessels, which are much more numerous, and 
equably distributed ; hence the circulation downwards 
is probably impeded, and the tendency of the graft to 
evolve its fruit)-bearing buds increased. 

In transplanting trees, if tlieir size is at all consider^ 
able, they should be stripped of a portion of their 
branches and leaves by cutting ; for they must in tdie 



384 AGRICULTURAL CHEMISTRY. 

process of removal from the soil lose a great part of 
their roots and fine radical fibres; and supposing all 
their leaves remaining^ they would die from exhaustion 
of their moisture by the great evaporating surface. 

By lopping trees more nourishment is supplied to the 
remaining parts ; for the sap flows laterally as well as 
perpendicularly. The same reasons will apply to ex- 
plain the increase of the size of fruits by diminishing 
the number upon a tree. 

As plants are capable of amelioration by peculiar 
methods of cultivation, and of having the natural term 
of their duration extended ; so, in conformity to the 
general law of change, they are rendered unhealthy by 
being exposed to peculiarly unfavourable circumstances, 
and liable to premature old age and decay. 

The plants of warm climates transplanted into cold 
ones, or of cold ones transplanted into warm ones, if 
not absolutely destroyed by the change of situation, are 
uniformly rendered unhealthy. 

Few of the tropical plants, as is well known, can be 
raised in this country, except in hot-houses. The vine 
during the whole of our summer may be said to be in a 
feeble state with regard to health ; and its fimt, except 
in very extraordinary cases, always contains a super- 
abundance of acid. The gigantic pine of the north, 
when transported into the equatorial climates, becomes 
a degenerated dwarf; and a great number of instances 
of the same kind might be brought forward. 

Much has been written, and many very ingenious 
remarks have been made by different philosophers, upon 
what have been called the habits of plants. Thus, in 
transplanting a tree, it dies or becomes unhealthy, un- 
less its position with respect to the sun is the same as 
before. The seeds brought from warm climates germi- 



LECTURB V, 385 

nate here much more early in the season than the same 
species brought from cold climates. The apple-tree 
from Siberia, where the short summer of three months 
immediately succeeds the long winter, in England 
usually puts forth its blossoms in the first year of its 
transplantation, on the appearance of mild weather ; 
and is often destroyed by the late frosts of the 
spring. 

It is not difficult to explain tbis principle go inti- 
mately connected with the healthy or diseased state of 
plants. The organization of the germ, whether in 
seeds or buds, must be different, according as more or 
less heat or alternations of heat and cold have affected 
it during its formation ; and the nature of its expansion 
must depend wholly on this organization. In a change- 
able climate the formations wiU have been interrupted, 
and in different successive layers. In an equal tem- 
perature they will have been uniform ; and the opera- 
tion of new and sudden causes will of course be severely 
felt. 

The disposition of trees may, however, be changed 
gradually in many instances; and the operation of a 
new climate in this way be made supportable. The 
myrtle, a native of the south of Europe, inevitably dies 
if exposed in the early stage of its growth to the frosts 
of our winter ; but if kept in a green-house during the 
cold season for successive years, and gradually exposed 
to low temperatures, it will, in an advanced stage of 
growth, resist even a very severe cold. And in the 
south and west of England the myrtle flourishes, pro- 
duces blossoms and seeds, in consequence of this pro- 
cess, as an unprotected standard tree ; and the layers 
from such trees are much more hardy than the layers 
from myrtles reared within doors. 

you vn. s 



386 AGRICULTURAL CHSMISTRT. 

The arbutus, probably originaUy from similar cultiT*- 
tioD, has become the principal ornament of the lakes of 
the south of Ireland. It thrives even in bleak mountain 
ntuations; and there can be little doubt but that the 
o&pring of this tree, inured to a temperate climate, 
might be easily spread in Britain. 

The same principles that apply to the effects of heat 
and cold will likewise apply to the influence of moisture 
and dryness. The layers of a tree habituate to a 
moist soil will die in a dry one ; even though such a 
soil is more &vourable to the general growth of the 
species. And, as was stated, p. 331, trees that have 
been raised in the centre of woods are sooner or later 
destroyed, if exposed in their adult state to blasts, 
in consequence of the felling of the surrounding 
timber. 

Trees, in all cases in which they are exposed in high 
and open situations to the sun, the winds and the rain, 
as I just now noticed, become low and robust, exhibit- 
ing curved limbs, but never straight and graceful trunks. 
Shrubs and trees, on the contrary, which are too much 
secluded from the sun and wind, extend exceedingly in 
height, but present at the same time slender and feeble 
branches; their leaves are pale and sickly, and in 
extreme cases they do not bear fruit. The exclusion di 
light alone is sufficient to produce this species of dis- 
ease, as would appear from the experiments of Bonnet. 
This ingenious physiologist sowed three seeds of the 
pea in the same kind of soil : one he suffered to remain 
exposed to the free air; the other he enclosed in a tube 
of glass ; and the third in a tube of wood. The pea 
in the tube of glass sprouted, and grew in a manner 
scarcely at all different from that under usual circum- 
stances ; but the plant in the tube of wood, deprived of 



LECTURE V. 387 

lights became white and slender^ and grew to a much 
greater height 

The plants growing in a soil incapable of supplying 
them with sufficient manure^ or dead organized matter, 
are very generally low, having brown or dark green 
leaves, and their woody fibre abounds in earth. 
Those vegetating in peaty soils, or in lands too co- 
piously supplied with animal or vegetable matter, rapidly 
expand, produce large bright green leaves, abound in 
sap, and generally blossom prematurely. 

Where a land is too rich for com, it is not an uncom- 
mon practice to cut down the first stalks, as by these 
means its exuberance is corrected, and it is less likely 
to &11 before the grain is ripe : excess of poverty, or of 
richness, is almost equally fatal to the hopes of the 
farmer ; and the true constitution of the soil for the 
best crop is that in which the earthy materials, the 
moisture and manure, are properly associated ; and in 
which the decomposable vegetable or animal matter 
does not exceed one-fourth of the weight of the earthy 
constituents. 

The canker, or erosion of the bark and wood, is a 
disease produced often in trees by a poverty of soil ; 
and it is invariably connected with old age. The cause 
seems to be an excess of alkaline and earthy matter in 
the descending sap. I have . often found carbonate of 
lime on the edges of the canker in apple trees; and 
ulmin, which contains fixed alkali, is abundant in the 
canker of the elm. The old age of a tree, in this 
respect, is fidntly analogous to the old age of animals, 
in which the secretions of solid bony matter are always 
in excess, and the tendency to ossification great 

The common modes of attempting to cure the canker 
are by cutting the edges of the bark, binding new bark 

s 2 



$88 AGRICULTURAL CHBXISTRT. 

upon ity or laying on a plaster of earth: bot 
methods, though they have been much extcXLeA, pro* 
bably do very little in producing a regeneration of the 
pari* Perhaps the application of a weak acid to the 
canker might be of use ; or, where the tree is of great 
value, it may be watered occasionally with a Yciy 
diluted acid. The alkaline and earthy nature of the 
morbid secretion warrants the trial; but circmnstanoca 
that cannot be foreseen may occur, to interfere with 
the success of the experiment 

Besides the diseases having their source in the con- 
stitution of the plant, or in the unfiEivourable operatum 
of external elements, there are many otl^rs perhaps 
more injurious, depending upon the operations and 
powers of other living beings ; and such are the most 
di£Scult to cure, and the most destructive to the labours 
of the husbandman. 

Parasitical plants of different species, which attaoh 
themselves to trees and shrubs, feed on their juices, 
destroy their health, and finally their life, abound in all 
climates ; and are, perhaps, the most formidable of the 
enemies of the superior and cultivated vegetable species. 

The mildew, which has often occasioned great havoc 
in our wheat crops, and which was particularly destmc* 
tive in 1804, is a species of fungus, so small as to re* 
quire glasses to render its form distinct, and rapidly 
propagated by its seeds. 

This has been shown by various botanists; and the 
subject has received a fiill illustration from the le* 
searches of the late ever-to»be-lamented Sir Joseph 
Banks. 

The fungus rapidly spreads from stalk to stalk, fixes 
itself in the cells connected with the common tabes, 



LSCTUBE y. 389 

aad carries away and consumes that nouriahment which 
should have been appropriated to the grain. 

Various remedies have been proposed for this disease. 
The Rev. Dr. Cartwright states that he has successfully 
treated it, by the application of a solution of salt, by a 
common gardening pot, to the stalks of the com. This 
18 a subject worthy of the most minute investigation; 
and all methods should be tried which promise to era- 
dicate so great an evil. As the fungus increases by the 
difiusion of its seeds, great care should be taken that 
no mildewed straw is carried in the manure used for 
com ; and in the early crop, if mildew is observed upon 
any of the stalks of com, they should be carefully 
removed, and treated as weeds. 

The popular notion amongst farmers, that a barberry- 
tree in the neighbourhood of a field of wheat often 
produces the mildew, deserves examination. This 
tree is frequently covered with a fungus, which, if it 
should be shown to be capable of degenerating into the 
wheat fungus, would ofier an easy explanation of the 
effect. 

There is some reason to believe, firom the researches 
of Sir Joseph Banks, that the smut in wheat likewise 
is produced by a very small fungus which fixes on the 
grain: the products that it affords by analysis are 
similar to those afforded by the puff-ball ; and it is diffi- 
cult to conceive, that without the agency of some 
organized structure, so complete a change should be 
affected in the constitution of the grain. 

The mistletoe and the ivy, the moss and the lichen, 
in fixing upon trees, uniformly injure their vegetative 
processes, though in very different degrees. They 
are supported from the lateral sap-vessels, and de<- 



390 AGRICULTURAL CHEMISTRY. 

prive the branches above of a part of their nourish- 
ment 

The insect tribes are scarcely less injurious than the 
parasitical plants. 

To enumerate all the animal destroyers and tyrants 
of the vegetable kingdom, would be to give a catalogue 
of the greater number of the classes in zoology. Every 
species of plant almost is the peculiar resting-place or 
dominion of some insect tribe ; and from the locust, 
the caterpillar, and snail, to the minute aphis, a won- 
derful variety of the inferior insects are nourished, and 
live by their ravages upon the vegetable world. 

I have already referred to the insect which feeds on 
the seed-leaf of the turnip. 

The Hessian fly, still more destructive to wheat, has 
in some seasons threatened the United States with a 
famine. And the French government in 1813 issued 
decrees with a view to occasion the destruction of the 
larvae of the grasshopper. 

In general, wet weather is most favourable to the 
propagation of mildew, funguses, rust, and the small 
parasitical vegetables ; dry weather, to the increase of 
the insect tribes. Nature, amidst all her changes, is 
continually directing her resources towards the produc- 
tion and multiplication of life ; and in the wise and 
grand economy of the whole system, even the agents 
that appear injurious to the hopes, and destructive to 
the comforts, of man, are, in fact, ultimately connected 
with a more exalted state of his powers and his condi- 
tion. His industry is awakened, his activity kept alive, 
even by the defects of climates and season. By the 
accidents which interfere with his efforts, he is made to 
exert his talents, to look farther into futurity, and to 



LECTURE V. 3&1 

consider the vegetable kingdom not as a secure and 
unalterable inheritance, spontaneously providing for hit 
wants ; but as a doubtful and insecure possession, to be 
preserved only by labour, and extended and perfected 
by ingenuity. 



END OF VOL. Vn. 



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